Ridding peer review of potential bias

Forensic investigation must be as thorough and objective as scientific research.  Peer review in science ensures that the research is well done.

Unfortunately, peer review in forensic work is not carried out very often.  And when it is there is a risk of bias in how it’s done.  This in spite of strict civil procedure rules governing experts and their reports.


Peer review in science is a process of evaluating scientific work, by an expert or a group of experts in the related field.  The scientific worker may or may not know the reviewer(s) – a blind peer review.  Similarly, the reviewer may or may not know the worker. (after Ref. 1 and Dr. Google)

Bias, or unreasoned judgement, can be blatant, or it can be unintended, sneaking up on us out of the ether. (Refs 2, 3 and 4)

Getting rid of bias in peer review is essential to forensic investigation.


The penny dropped for me on a better way compared to current practice when I got an e-mail from a reader, Ruth Corbin, after she read a blog I posted on peer review.  (Refs 5, 6)  A quick reply to Dr. Corbin included my initial thoughts on how I think we can get rid of bias.  These are bulleted below including some additional thoughts.

At present, experts investigate the cause of a problem.  They write a report on their investigation and findings.  The expert’s report goes to their client, the insurance claims adjuster or the civil litigation lawyer, and from there to the court or dispute resolution tribunal.  The investigation and report are seldom peer reviewed.  Except in a sense when they are rebutted by the expert for an opposing party.

Just how unbiased is the rebuttal report?  If phraseology in some reports is any indication, not much.

(You’ve all seen this phraseology, I’m sure.  Just to be really sure though, I’ll update this blog in future with some examples)

A peer review doesn’t have to be a crude denunciation or vetting of an expert’s work.  We can get rid of blatant bias.  We’re all here to serve the judicial and dispute resolution processes.  Finding errors and omissions and fixing them serves that purpose.

A peer or rebuttal review a little closer to that in science would help, one that involves the expert as little as possible in the organizing of a peer review of his work.  I think peer review procedures like the following will help, in decreasing order of preference:

  • The court or tribunal retains the peer reviewer independent of the expert or his client.  This in the spirit of peer review in the scientific community.
  • All the experts engage in “hot-tubbing” session, give their evidence concurrently and agree a joint report. (Refs 2, 7)
  • The lawyer or adjuster retains a peer expert to review his work.  Because s/he wants a thorough and objective explanation of issues unfamiliar to the court or tribunal.  But third in preference because the lawyer does have his interests.
  • The expert retains a peer reviewer.  Because she would like to think they have done thorough work and reasoned well, particularly in the more empirical applied sciences like some medical and engineering specialties.  But fourth in preference because perception is everything in some fields of study.  An expert hiring someone to check his work might not look good.
  • The rebuttal expert peer reviews the expert’s work.  I include this procedure because it’s a procedure that is sometimes followed.  It can work if the rebuttal expert pushes back against bias.
  • No peer review at all of any kind.  The procedure assumes the expert’s work is thorough and objective and unbiased.

I believe the risk of bias is low when the court or dispute resolution tribunal arranges the peer review and high when the rebuttal expert does this.


We can get rid of some or almost all bias in peer review of forensic investigation and expert services.  There are several methods for doing this.  What we chose will reflect our commitment to change and what we’re prepared to accept.  We’re accepting a lot of potential bias now.


  1. Merriam-Webster dictionary
  2. Biased experts cured with a soak in the “hot tub”.  A blog posted January 31, 2017 at www.ericjorden.com/blog
  3. Expert witness forum looks at bias and other touchy subjects in forensic work. Posted March 8, 2018
  4. Are experts being broadsided by bias unbeknownst to them?  Posted April 12, 2018
  5. A Bundle of Blogs: On the need for peer review in forensic engineering and expert services.  Posted November 29, 2019
  6. Corbin, M.Sc., Ph.D., LL.D., Ruth M., Chair, Corbin Partners Inc, and Mediator, Corbin Estates Law, Toronto
  7. “Hot-tubbing” experts reduce the cost of civil litigation and ensure objectively.  Posted March 31, 2018


Differential diagnosis in medicine and forensic investigation, and soft, initial thoughts on cause

The phrase “differential diagnosis” caught my eye recently in light of some tendency in forensic engineering for the injured party to take the expert’s initial thought on cause as gospel and run with it.

Yet the forensic expert’s initial thought – an initial hypothesis – is based on just a little evidence and likely, quite subjective evidence.  For example, a briefing by the client, a  read of some documents and perhaps a walk-over survey of the accident or failure site.

Sometimes that thought/hypothesis is subject to revision like happens in the scientific method – and an embarrassment to all concerned if counsel decides to take the case or the claims manager agrees a settlement.

(Scientific method: A method or procedure that has characterized natural science since the 17th century, consisting in systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses. Ref. 1)

Differential diagnosis is a medical process.  It occurred to me that forensic experts could learn from medical doctors.

Differential diagnosis is the development of a list of possible medical conditions that might explain a patient’s symptoms.  The list goes from the most likely and urgent at the top to the least at the bottom.  The process involves several phases like forensic investigation involves several stages.  The early phases/stages are subjective in nature.  The process is well developed in medicine as explained by a friend and also Dr. Google. (Refs 1 and 2)

The phases of a differential diagnosis and their similarity to a forensic investigation are a little like the following:

Phase #1 Take history

In medicine, take a history from the patient about what she’s experiencing.  Interrogate and ask questions like a detective.  Try to figure out what’s going on.

In forensic work, take a briefing from the injured party or their counsel or claims manager about their slip and fall accident or the damage to their building.  Ask lots of questions.  Read existing documentation.  Consider different categories of accidents or failures.

Phase #2 Physical examination

Look, feel and listen.  Take the patient’s pulse and measure his blood pressure.  Examine him orally.  Listen to his chest (with a stethoscope).  Do a percussive examination (tap body with fingers and note the sound)

Walk over the site and visually examine the accident or failure scene and the structures there.  Measure and determine the condition of the structure before and after the failure.  Photograph and measure features characterizing the scene.  Take aerial video of the scene from a drone.  Excavate test pits and note the subsurface conditions.  Carry out initial skid resistance tests of the floor at a slip and fall accident. 

Phase #3 Additional investigative tests

Carry out additional tests like blood work, X-rays, MRIs and stress tests.

Take samples and do laboratory tests of the physical properties of materials that failed.  Do field tests and sample and test the physical properties of the soil in the field and laboratory.  If necessary, do additional skid tests of the floor.

Phase #4 Data analysis and interpretation

Analyse data and test results and identify conditions that could account for the patient’s symptoms.  List from most likely to least likely – the differential diagnosis.  Look at the most probable diagnosis at the top of the list then go back to Phase #3 and order more tests to confirm depending on how confidant you are.

Study the data, look at how different pieces of data relate and support one another and relate to possible causes of the personal injury or the crane or building collapse.  Identify the probable cause(s) of the injury or collapse.  If necessary, return to the site to check and confirm earlier findings.

Phase #5 Treatment

In medicine, prescribe a treatment of the condition with medicines, life style changes, diet, etc.  Monitor the condition and if improves good.  If no improvement, consider the dosage of medicines and the extent of other changes.  If none or not much go back to the previous phase and reconsider the differential diagnosis.  Treatment is the prescription, the plan in SOAP. (Ref. 3)

In forensic work, report the most probable cause of the accident or failure.  Recommend how the damage can be fixed and the cause of the accident or failure eliminated.


I see the differential diagnosis process as an elaboration of the SOAP process that is also followed in medicine: (Ref. 3)

1. Gather Subjective data.  Take a history from the patient in medicine and a briefing on the problem in engineering.  Reflect on why the patient is hurting and the different categories of structural failure in engineering.

2. Get some Objective data.  Like blood work and X-rays in medicine and measurements and field and laboratory tests in forensic investigation.

3. Analyse the data.  Study, identify and list the different medical conditions indicated by the data that could account for the patient’s symptoms.  And in forensic work, the different causes that could account for the personal injury or the crane or bridge collapse.  The list is the differential diagnosis in medicine and the possible causes in a forensic investigation, going from the most likely cause at the top to the least likely at the bottom.

4. Prescribe treatment.  For example, identify life style changes, diet and/or medications to fix the medical condition and make the symptoms disappear.  In forensic work recommend how the damage can be repaired and the cause removed.


Can you imagine the embarrassment to the medical doctor and the pain for the patient if s/he prescribed treatment based on the results of Phase #1 of the differential diagnosis process and he was wrong and the patient dies?  Everybody gets in trouble.

Fortunately, that doesn’t happen often in medicine.  Unfortunately it happens at times in forensic work – the client runs with the expert’s initial thoughts on cause.  A few years ago, an expert noted the occasional pressure on an expert during a forensic investigation to find support for those initial thoughts.


So, the next time you’re getting a medical check-up think about the forensic expert and hope the doctor doesn’t go with his initial thoughts on the cause of your symptoms.  And if you’re the forensic expert, go out of your way to help your client, the injured party, understand that an initial thought on cause is not necessarily a final diagnosis.  It’s at the front end of the subjective-data-collection-stage and a soft thought.


  1. Dr. Google
  2. Personal conversation with Dr. J. Nasser, Halifax, a retired ear, nose and throat surgeon and a former dentist
  3. Using SOAP notes in forensic engineering investigation.  Posted February 6, 2014



A Bundle of Blogs: Aerial video of insurance and forensic sites taken with cameras mounted on drones

Aerial video of a site taken from a low flying drone is one of the best insurance and forensic investigative methods that I’ve used in a long time.  I’ve had excellent results since learning of this method in 2014 and my enthusiasm continues to grow – the following 15 blogs attest to that.

I attempted in the blogs to explain and demonstrate the worth of this method.  After 15 blogs it seemed time to bundle them together.  Particularly after the watershed development explained in Blog #1 below that enables me to plan a virtual flight over a failure or accident site days in advance and miles away.  New software and Google Earth make it happen.  But it can be very simple and low tech with a kid’s drone as explained in Blog #5.

What we’re doing is simple enough – taking aerial video of a site and analyzing it for data and evidence.  What’s different today is that we’re getting video from way down low, 10s to 100s of feet above a site.  In the past it was only possible from up high, many 1,000s of feet, from high flying planes.  Close to the ground, the detail captured with high resolution cameras mounted on drones is something else.

The following blogs describe what’s going on.  Several are of sites involved in insurance and forensic engineering investigations – see Blog #12 of an environmental investigation in the U.S.  Other blogs in the Bundle indicate the potential of up close aerial video.

  1. It’s here, cost effective, efficient aerial video for forensic investigation!  Posted October 8, 2019
  2. The drone will get the alleged killers, if they’re there.  Posted July 31, 2019
  3. What’s wrong with this (sinkhole) picture near Vancouver?  Posted February 20, 2019
  4. Reliable forensic evidence from drone photography: Aerial photography from way down low.  Posted October 31, 2018
  5. A kid’s toy drone can photograph the site of an engineering failure, a personal injury or a traffic accident.  Posted September 12, 2018
  6. Getting evidence in slip and fall accidents and building failures with video taken from a drone.  Posted August 9, 2018
  7. Drone video as a forensic technique is joined by drone photography as an art form.  Posted August 2, 2017
  8. “Unexpected” evidence and the importance of drone photography in forensic investigation.  Posted July 19, 2017
  9. Conference call on a “drone flight” reduces cost of civil litigation.  May 18, 2017
  10. Getting evidence with a low cost, low tech drone flight over a forensic site.  Posted March 31, 2017
  11. “Crewing” on a forensic drone flight.  Posted October 4, 2016
  12. U.S. civil litigation lawyer on using air photos in environmental litigation.  Posted November 18, 2015
  13. Fixed wing drones – another tool in forensic engineering investigation.  Posted November 4, 2015
  14. New forensic aerial photographic method proving extremely valuable.  Posted January 30, 2015
  15. A picture’s worth a 1000 words possibly many 1000s in forensic engineering with a new aerial photographic technique.  Posted January 15, 2014


It’s here, cost effective, efficient aerial video for forensic investigations!

It sounds like a commercial, but I was excited when I learned that you can now plan a drone flight and aerial video of a site from your office armchair.  Then see the virtual flight in 3D on Google earth – all before you drive to the site and days before the real flight.

You can get a preview of video taken during a virtual flight then, with a click of the mouse, change the drone’s flight path, speed and altitude, and the video camera angle.  Do this as often as you like, after as many virtual flights as you like, till you’re happy you’ve captured what you need – all from your armchair.

Needless to say, you can also plan as many different flights as you like over and around your accident, building or crane collapse site.

Then – after the client reviews all virtual flights on a CD and likes what he sees – drive to the site and fly it for real.  New software and Google earth make it happen.

Robert Guertin, Dartmouth, drone pilot and photographer gave me a demonstration a few days ago and it was impressive. (Ref. 1)


I retain Robert now to take aerial video from a drone of all sites where I’m carrying out a forensic investigation.  In the past we drove to the site with a drone fitted with a video camera and flew the site, seeing it for the first time from the air.  We made several flights – on site, not from an armchair – till we got the scene and the surrounding terrain on video in the detail I needed.

I got good data – I’m in awe about the worth of this forensic technique; including this one, I’ve posted 15 blogs on low level aerial video since 2015.  But sometimes I would get back to the office and after studying the video and doing some terrain analysis find that I might have flown additional paths or one or two in a different way and got even better data.

(Terrain analysis is another valuable technique in engineering – particularly now with low level aerial video – which I’ll tell you about later.  The terrain and the flora hold secrets to what underlies the site and what’s happened there in the past)


But, now we plan my flights from an office armchair. The software engages Google earth and brings up a 2D picture of the site on Robert’s desktop.  We’ve all seen these Google earth pictures.  I plan a flight over our site marking the path with way points on the 2D picture – a click of the mouse for each point.

The software then allows me to specify the height of the drone, it’s direction (heading in aviation) and it’s speed at each way point.  I also specify the camera angle, the view I want of my client’s site.

We engage Google earth again and ask the software to export the flight path’s file to Google earth.  This gives a 3D Google earth image of our site with the flight path superimposed.  We then fly this virtual flight path from our armchairs.

I have a look at what we’re getting during the flight.  If I don’t like what I see we disengage from Google earth, tweak the flight specification at each way point and fly again.  When we get a virtual flight and video coverage that collects the data I need, Robert produces a video clip and I send it to the client for approval.

On the client’s approval we drive to the site, load the flight plan to the drone and video camera and fly the site.  The software sends the drone on all the virtual flight paths we specified and the camera on board takes real video.  The video is put on a disk and the field work is done.

You can imagine the cost effectiveness of this forensic technique.  You capture what you need at your site then study and analyse the data later in your office.  It’s easy, productive and fun.  Forensic engineering investigation doesn’t get much better than this.


Virtual Flight Demonstrations

Robert demonstrated this technique for me at three sites, sitting in an armchair in his office.

A wharf in Nova Scotia.  This was one of Robert’s for-real commissions.  The client wanted the wharf repaired.  Robert was asked to fly the site and video the wharf and it’s present condition.  He planned distant, middle distant and close-up video of the wharf with the drone flying specified virtual paths, some at tree top level and others at scary, wave top heights.

The client was then sent a CD of the virtual flights for approval.  This was got then Robert went to the site and flew it for real, same as he’s done for me several times.  I saw all of both the virtual and real flights over and around the wharf – there was little difference between the two – and they were good.

The Dartmouth waterfront.  Robert then planned a virtual flight in 3D along the Dartmouth waterfront in front of Admiralty house then flew it as I watched from my armchair.  He specified all the flight and camera parameters identified above same as he would do if someone wanted to design and construct a building on the waterfront.

My home and neighbourhood in Dartmouth.  Finally, if I wasn’t impressed enough already, just to be sure, he then designed a virtual flight and video of my home and neighbourhood and flew it, as I watched from my armchair in his office.


  1. Meeting with Robert Guertin, Videographer, photographer, drone pilot, Millenium Film and Video Productions Ltd., Dartmouth, Nova Scotia


Am I a civil engineering expert?

I was asked recently, “Are you a civil engineering expert?”

I thought, civil engineering is such a broad field of study how can anyone be an expert?  But then I realized I have knowledge in the field enabling me to form an opinion that will assist the fact finder.  I have degrees and experience in civil engineering and the fact finder doesn’t.  My knowledge is greater in some areas of civil engineering and less in others, but still greater than the fact finder’s.

I was also quick to realize that I had considerable knowledge relevant to the issue being discussed at the time prompting the question of me.  Gaining that knowledge over the years provided insight into some of the sub-disciplines of civil engineering that many civil engineers might not get.

(Civil engineering is a discipline that applies physical and scientific principles to the design, construction, and maintenance of the built and natural environments.  Everything you see around you in the course of a day.  Its history goes back 1,000s of years)

Civil engineering sub-disciplines

You might still wonder if I’m a civil engineering expert when you see a list of some of the sub-disciplines of civil engineering:

  • Structural engineering
  • Foundation engineering
  • Geotechnical engineering
  • Environmental engineering
  • Coastal engineering
  • Water resources engineering
  • Forensic engineering
  • Geomatics engineering
  • Construction engineering
  • Earthquake engineering
  • Industrial engineering
  • Hydraulic engineering
  • Municipal or urban engineering
  • Transportation engineering

So many, and there’s still others.  But, look how a civil engineer can learn about different sub-disciples and be quite useful to a trier of fact:

How we learn about the sub-disciplines

I studied land surveying for two years before studying civil engineering and was licensed as a provincial land surveyor on P.E.I..  My summer work and for a year after I graduated from engineering was construction surveying for municipal water supply and sewage collection pipeline construction.  I also assisted construction surveying for 1.5 years during construction of an oil refinery.

So, some good insight gained into refinery construction, municipal work and geomatics engineering, formerly known as survey engineering.

I did highway engineering design work for a year in Vancouver.  I also got introduced to geotechnical engineering in Vancouver that included field testing of the sub-grade soils along 200 miles of highway in the Yukon.  I did foundation design and structural engineering while in Adelaide, Australia, and geotechnical engineering investigation of embankment failures in Brisbane and northern Australia.

All relatively short periods of time but real good introductions to the sub-disciplines.

I’ve not done hydraulic engineering or industrial engineering but that’s okay; you can’t do them all even if you do a lot.  (I did investigate the ground conditions for construction of hydraulic structures like dams and canals)

I eventually specialized in geotechnical engineering and did graduate work in the U.K. where I practiced for three years then continued in Canada.

Geotechnical engineers investigate and identify the different layers of soil beneath a planned construction site and test and measure the physical properties of these materials.  The soil properties are then used by engineers to design foundations that will safely support the structure planned for the site.

Geo engineers also design and monitor construction of earthwork structures like embankments, filled ground and highway cut slopes.

They must talk with owners, architects, site engineers, environmental engineers, structural engineers, foundation engineers, construction engineers – all sub-disciplines of one kind or another – to learn about the structure that must be supported on the ground.

Structures like low- and high-rise buildings, roads, bridges, dams, canals, retaining walls, towers, wharves, harbours and breakwaters, earthwork embankments and highway slopes.

Civil engineers get informed

You can just imagine as the years go by, how a civil engineer becomes quite well informed about these engineering sub-disciplines, and the different structures forming the built environment we live in.

(Hope your eyes are not glazing over yet – it really is like this in civil engineering)

Geo engineers overlap with environmental engineers

If you work in geotechnical engineering it’s not too long before you’re overlapping with environmental engineering.  Environmental engineers have a big interest in everything to do with water in the environment.

Surface water and ground water (the water table) changes the physical properties of soil and rock.  Sink holes like those in Oxford, Nova Scotia are a prime example.  Gypsum bedrock will support foundations quite nicely when dry but dissolves when exposed to ground water.

If you work in geotechnical engineering it’s also not too long before you’re doing Phase I, II and III ESAs – Environmental Site Assessments.  As a civil engineer, I’ve done a few of these over the years.  There’s a lot of overlap between the geotechnical and environmental sub-disciplines.

Sub-disciplines connect with their co-sub-disciplines

It’s the same with the other sub-disciplines and how they connect with their co-sub-disciplines:

  • Foundation engineers learn something about geo work, structural engineering and environmental engineering:
  • Highway engineers learn about geomatic engineering, and quite a lot about geotechnical engineering because highways sit on the ground;
  • Municipal engineers learn about geo engineering too because pipelines are buried in the ground;
  • Many sub-disciplines learn a little something about environmental engineering because engineering the built environment alters the natural environment
  • Structural engineers soon learn about earthquake engineering
  • Coastal engineers learn about the requirements of foundation engineers and environmental engineers

It goes on and on, the inter-relationship of the civil engineering sub-disciplines.

The principal engineer

However, it’s important for a civil engineer to know when to assume the position of principal engineer. (Ref. 1)

Principal engineers coordinate the work of other engineers and specialists to a common goal – in forensic engineering, to determining the cause of a collapse or accident in the built environment.  A principal engineer might be directing the efforts of construction engineers, structural engineers, mechanical engineers and crane operators in removing the collapsed crane from the multistory building in Halifax. (Ref. 2)

I’m not qualified to do structural and construction engineering but can develop some of the parameters enabling them to do their work, particularly soil and rock properties for foundation design.  I am qualified in earthworks design and also done a lot of materials testing and site inspection (earthworks and concrete construction).

I’m certainly qualified in knowing when to step back into the position of principal engineer, and well out of the way of those who know better.  I know when to retain one or more of the sub-disciplines because I’ve worked with them.

For example

I investigated a nail gun accident a few years ago.  It was easy for me to check if the nail gun appeared to work properly because I used one when I built my house from the ground up.

But, were hidden parts of the nail gun worn?  I’m not a mechanical engineer so I retained a specialist in nail gun repair to take it apart and tell me.

Was it poorly designed or manufactured?  I was ready to retain specialists in these fields.

First however, I decided to have the victim re-enact the nail gun accident while I took a video.  I take a lot of pictures and video in my expert work and this was easy for me to do as principal engineer.  The video of the re-enactment was insightful to say the least.

In other cases, I retained a structural engineer to guide me in underpinning a structure.  I retained a specialist in concrete design to guide me in retaining wall design.  I’ve got a call to a structural engineer now about bracing a deck structure so it won’t fall over.

Family doctors as principal investigators

The concept of principal investigator is not unique to civil engineering.  The medical profession adopts this approach all the time.

Your family physician takes a patient history, does a physical examination, may order some tests and may refer you to a specialist if s/he sees a potential problem.  He would coordinate the investigations of the other doctors and specialists into the problem.  The specialists would carry out thorough investigations and explain their findings in detail.  (Ref. 3)

It’s similar in construction when a general contractors hires carpenters, electricians, plumbers and roofers to do a job.  The general is the principal, the trades are the specialists.


So, what did I say?

Thinking through all of the above got me comfortably to the stage of answering the question put to me, “Are you a civil engineering expert?”.  What do you think I said?


  1. Lewis, Gary L., Editor, Guidelines for Forensic Engineering Practice, American Society of Civil Engineers (ASCE) Reston, Virginia 2003
  2. Why do I think the crane collapsed in Halifax?, posted September 20, 2019
  3. Personal communique with Dr. J. Nasser, Halifax, NS. September, 2019

Advocates, insurers and property owners, become aware!

I initially thought Buyer beware! as a title for this blog but that would be a poor choice of words because you’re not at risk of being cheated when you retain a forensic expert.  You are at risk of thinking an expert knows everything

And related, also at risk of misunderstanding the tasks a forensic expert must carry out in conforming to good practice when investigating a failure or accident.  Misunderstanding leads to crankiness as experienced by a couple of my clients.

You need to learn a little something about these tasks.  And why s/he must do them, and why it’s difficult to estimate the cost of some of them.  If we follow the evidence, we don’t even know about some of these tasks until our boots are on the ground.

Learn something about the following:

  • The building or civil engineering structure involved in the expert’s work
  • The stages and tasks in a forensic investigation

Become aware of the following:

All buildings and civil engineering structures in the built and natural environments have basic components that experts can name for you.  For example, they all have foundations, and also beams and columns.  And do you know?  A structure’s basement – like your house basement, for example, or that of a multi-story building - is the most complicated component of all – not very glamourous, just the most complicated. (Ref. 1)

All forensic engineering investigations have basic stages and tasks that are described in simple, non-technical language on this site and in engineering guidelines. (Refs 2, 3 and 4)  Some examples: 1) The document-review stage, 2) The visual-examination-of-the-site stage, 3) The recording-the-as-built-condition-of-a-component state, 4) Noting the as-failed-condition-of-a-structure stage, and 5) In a slip and fall accident, testing-the-skid-resistance-of-a-floor stage.  And all are carried out to an engineering standard of care.

We can estimate the cost of known tasks with varying degrees of accuracy – from easy and accurate to very difficult and quite inaccurate. (Refs 5, 6)  It’s the unknown tasks that crop up when we follow the evidence and look under the next rock that cause grief for all parties involved in a dispute.

The following nice people thought I knew everything:

Example #1: A client was surprised that I met with a contractor on site and charged a fee for this.  I was there to brief the contractor on the project and confirm how he would tackle the several stages involving different structures.  It was somewhat of an exotic project and nowhere to be found in the engineering textbooks.  I can specify an end result but it behoves me to make certain the contractor knows how to get there.

“I thought you knew everything!” my client remarked.  A nice way to be seen but we don’t know everything – we do know how to figure things out though.

Example #2: Another time a client was surprised when I charged for “researching” an issue -  safety criteria in a slip and fall accident.  There’s little guidance in the building code on this type of problem but lots of literature in North America and Europe.  I had to figure out how it applied to my particular case.  Again, “I thought you knew everything!”.  Nice thought.

Example #3: I’m trying now to determine if the site of an old fuel oil spill is still contaminated.  The spilling stopped about 27 years ago when the underground storage tanks were removed.  It’s fairly easy to learn the direction the oil flowed when it was carried away by the groundwater.

It’s something else to learn where the oil ended up and if the ground is still contaminated at that location.  I do know that natural attenuation has reduced the amount of oil in the ground but whether or not to an acceptable level is difficult to determine.

Natural attenuation is a complex process and there’s little or no expertise readily available because the problem doesn’t crop up often.  Should I get compensated for trying to find an expert in eastern Canada, the USA or farther afield because “I don’t know everything”?

(Natural attenuation involves microorganisms in soil eating the oil – it’s food to them.  There are five processes in natural attenuation but this is a main one)

Example #4: Somewhat related were the geotechnical investigations I carried out for new wharf and breakwater construction in harbours on Canada’s east coast.  About 27 investigations over several years.  My clients wouldn’t cover my expenses to travel to a harbour and reconnoiter conditions before estimating the cost of the work.

For example, reconnoiter the sea conditions we had to work in – sometimes quite exposed and dangerous -, investigate coastal conditions from which we had to launch a barge with a drill rig onboard, and check out the possible foundation soil conditions as exposed along the coast.

Surely I would not be expected to “know everything” about a harbour without seeing it and talking with the local fishermen?  And surely It’s not unreasonable to charge a fee for this?


When I suggest you learn a little something, I don’t mean you should learn a lot and pass a test.  Just gain some understanding and become aware of the tasks an expert must carry out, and to the standard of care for the time and place.

The recent case, Example #1, where I met the contractor on site consisted of seven big tasks.  Three quite large, different tasks plus three less-big tasks that prepared site conditions for a main task.  The main task also had a poorly defined scope that made matters worse.  All big tasks with expertise in the area but none that are done on even a half yearly basis, year after year.  And when the seven tasks were lumped together, this type of seven-big-task project was unusual for this area.

I would hardly expect you to learn much about a project like this but learn something and that it’s demanding of an expert’s time, including figuring-out and occasional research time.

Learn a little something about “the nature and methods of forensic engineering investigation” like it says in the masthead of this blog site.  Also the structure(s) involved and its components.  Forensic experts can give you a good understanding in most cases, except when we’ve got to follow the evidence and don’t know what we’re going to find until we get there.


  1. Swinton, Michael, NRC-IRC and Kesik, Ted, PhD, University of Toronto, Performance Guidelines for Basement Envelope Systems and Materials, Research Report 199, pp 185, National Research Council, Canada October 2005
  2. Steps in the Forensic Engineering Investigative Process With an Appendix on Costs.  Posted July 15, 2013
  3. American Society of Civil Engineers (ASCE), Guidelines for Failure Investigation, 1989
  4. Janney, Jack R., Guide to Investigation of Structural Failure, ASCE, 1986
  5. Difficulty Estimating the Cost of Forensic Engineering Investigation.  Posted July 23, 2013
  6. Why the Difficulty Estimating the Cost of Forensic Engineering Investigation?  Posted September 1, 2013


  1. Lewis, Gary L., Guidelines for forensic engineering practice, ed., ASCE 2003
  2. A Bundle of Blogs: How to Manage the Cost of Civil Litigation Involving Experts.   Posted August 31, 2017



Reliable forensic evidence from drone photography; Aerial photos from way-down-low

I continue to be excited about using drone photography during forensic investigations.  The engineer and former land surveyor in me loves the wealth of accurate data in photographs taken a few 10s to 100s of feet above a site where a structure failed or a person was hurt.

We’ve always had photogrammetry in engineering – using photographs taken from airplanes flying many 1,000s of feet above the earth to identify and measure features on the ground.- but we get more and better data from drone photos and get it quicker and cheaper.  The potential uses are something else:

Use #1: Investigating traffic accidents: An engineering colleague routinely sends a toy drone aloft, a 100 feet or so, and takes a photograph of a traffic accident site that he is reconstructing. (Ref. 1)  He sees his site from this angle right away and it guides his investigation as he does his field work.  He can also get a print of his drone photo for his engineering report..

Use #2: Conferring with clients: I conferred with a client a few months ago while both of us had a CD of aerial video of his property uploaded on our computers.  I had mailed the CD to him a few days earlier.  He commented on features on the ground relevant to my investigation of his failure.

In one case he gave the history of the ground at one location – cows drank from a former dug well there in the past – that was important in confirming the depth to the ground water beneath the site.  At the time I couldn’t quite believe what i was hearing about the cows and the dug well – there was no evidence of this when I was on site..

Use #3: Getting data on a site: I emailed a drone photograph to a client recently and asked him to identify the location of buried structures on his property.  Structures like two underground fuel oil storage tanks (USTs), – which leaked oil in the past – a drilled water well, two dug wells, a septic tank and a disposal field.  He did this then emailed the marked up photograph back to me a few hours later.  He used Paint, a program on PC computers.  It was all so quick and inexpensive.

Use #4; Getting BIG Data:: The height or altitude of the drone above the ground when a photograph was taken has always been of interest to me.  Robert Guertin, Halifax who takes my aerial video, found a program that gives a wealth of data on each photograph.  The data includes the height of the drone when the photograph was taken, angle of the photo shot below the horizon, bearing of the view with respect to North and the GPS location, all important data in forensic work.

Use #5: Getting low cost data:  I get the scale of drone photographs now from the known size of objects in the photographs.  Like the length and width of a building or the distance between the lines on a highway.  The scale of the photograph I sent to my client a few days ago that he marked up with Paint is 1″ = 40′.

I can check the scale of a drone photograph by setting out ground control before taking drone photographs, like photogrammetry-of-old.  Ground control is nothing more than points set out on the ground a known distance apart and height above sea level.  I used sheets of white paper to mark points on a site I was investigating in Cape Breton.

Use #6: Photographing hard to get at damage: I recently suggested to a firm who needed an expert that we could record the condition of a damaged wall with a drone photograph.  Later I could measure and analyse the damage in detail and get an idea of the cause – measuring like I do now of the ground but of a vertical surface rather than a horizontal surface.  No step ladders, staging, labour and lots of expensive time needed.  .

Use #7 Replacing expensive site surveys:  The drone photograph with a known scale is certain to replace the need in the future for a site survey by a land surveyor, and be far more detailed, less expensive and quicker.  Site surveys measure the size, location and elevation of objects and features on the ground.  Conventional site surveys can be time consuming and expensive.

Use #8: Seeing a site in 3D: I’m working with Robert to see if we can get a stereo pair of drone photographs of a failure site and using these to view a site in 3D like we’ve always done in photogrammetry-of-old.  Software likely exists now for viewing drone photographs in 3D.  If it’s out there we will find it and I will use it during my forensic investigations.  In the meantime we’re trying to do it ourselves.

(A stereo pair are two photographs overlapping by about 60%.  When viewed with a stereoscope – sort of like eye glasses – the site appears in 3D)


What more do you want from simple drone photographs?  Name it and the potential for getting it.is almost guaranteed.  Honestly, with all due respect, you or your expert would be remiss if you did not get drone photos of your site.  Your expert would not be conforming to the changing forensic investigative standard of care.


  1.  A kid’s toy drone can photograph the site of an engineering failure, a personal injury or a traffic accident.  Posted September 12, 2018



The two solitudes of expert services

Take your pick: An expert from the great majority represented by Ruth Corbin’s pilot study of 152 experts, or an expert from the fringe, (Refs 1 and 2)

The study found that the majority of experts know they’re serving the court, not the lawyer who retains them nor the lawyer’s client, and they continue to swear oaths to that effect.  The study was carried out because the judicial system continues to disbelieve them.

Fringe experts believe they are serving the lawyer and his client, not the judicial process.  This to the extent that some want to know upfront the technical issues as perceived by the lawyer – no mention of technical issues that the expert might identify – and how much budget money they got.  These questions during a first telephone call don’t resonate well.  I wouldn’t call these experts hired guns USA style but perhaps treading close Canadian style.

The “two solitudes” came to mind when I was chatting with one fellow and this fringe characteristic was reflected in his comments when the question of who we serve came up..  When i asked he was adamant that experts serve the lawyer not the judicial system.

Fringe example #1: Later this chap asked me to join him in responding to a lawyer’s need for an expert to investigate the cause of damage to a structure.  I didn’t think much about it at the time but he only casually referred to the lawyer by his first name as someone he knew, briefly mentioned another party involved and identified the location of the structure.

Based on my colleague’s description of the problem as he was briefed by the lawyer the cause was obvious, an easy initial hypothesis.  I had investigated this type of problem often enough over the years and it’s written up in forensic engineering guidelines on typical civil engineering failures and their cause.

i agreed to join him help resolve the dispute.  He would manage the case he said and I would investigate and confirm the cause of the problem.  He asked and I updated my CV over a weekend and sent it off to him on the Monday, only to learn he had responded to the lawyer on the Friday sans my CV but including his.

On reading his response to the lawyer I saw brief mention of my name.  When I asked he said he would send my CV when the lawyer asked for it.  I also asked several times over the next few weeks for a copy of his CV as presented and the name of the lawyer and his firm but he never gave me this information.  Months later he explained, “With deference, I’m not going to give you his name.  He called me.”.  Tricky, eh?

He’s heard nothing since from the lawyer.  I can’t help but think the lawyer’s smart enough to know my colleague’s engineering background hardly qualifies him to investigate this type of failure.

Nor can I help but think I witnessed fringe behaviour.  This chap is pleasant, well educated and experienced and I’ll consider working with him in the future, for the benefit of the judicial system, but he’s a bit tricky as I learned and we’ll get things out in the open at the get-go.

But, on second thought, I don’t know if perception is everything and I’m seen to be associating with a tricky, fringe expert.  Another forensic engineering colleague on recounting this case to him was quick to remind me of the perception issue.

Following are a few more fringe cases to ensure that you know there is a fringe solitude to expert services.

Fringe examples #2 and #3: I read two expert engineering reports by separate experts, one on the stability of a fill slope and the other on a slip and fall accident.  I cringed at the bias exhibited by the phraseology in both cases in favour of the experts’ clients.  Crass in one case.

You might say there’s a subjective element in an assessment of bias and that’s true.  But I feel more confidant in my subjective assessment after reading about the eight main biases in engineering. (Ref. 3)

I’ve also read and written a lot of engineering reports, research papers and blogs/essays over the years and I sure do know the difference between objective and biased phraseology.  Think most of us do.

I’m also comfortable with the objective evidence in both cases.  In the fill slope case, the expert did not get out of his car to see the large pieces of construction debris at the toe of the slope threatening the stability.  The debris included organic matter like tree stumps that rot away in time and cause a slope to subside a lot.

And in the case of the slip and fall accident, quite apart from his phraseology, the expert’s comments indicated he did not know the standard of care existing in the area for investigating the skid resistance of the floor at an accident site.

(Skid tests are coefficient of friction tests like in high school physics)

(A fill slope is the slope the surface of the soil or another material slumps down to when it’s piled on the ground.  A cut slope is the slope soil takes when we cut into or excavate the ground.  We see cut and fill slopes everywhere along our highways)

Fringe example #4: Would you like to know about a second slip and fall accident that exhibited fringe behaviour?  But, to cut the engineer some slack, possibly because he was new to the expert services arena.

An engineer, a five hour drive from the accident scene, decided the cause of the accident from pictures provided by his client.  He did not travel to the accident site and examine it firsthand nor carry out skid tests.  That would have added to the cost of the forensic investigation.  The judge dismissed the expert’s evidence.

Fringe example #5: Would you like a fifth fringe case; actually a fringe expert?  At least to some extent a fringe expert.  Years ago I heard an expert remark that he “…knows how to work a case up”.  Work it up into a “…juicy case…”.

Is my years-ago colleague practicing near the fringe?  Possibly.  He is good though in his area of expertise and still practising suggesting he’s impartial enough.  The last thing a lawyer wants is an expert that can be made a fool by the judicial process.  My colleague would have gone by the wayside years ago if he was a blatant fringe expert.

There’s no question the great majority of experts serve the judicial system and do this objectively.  Read Ruth Corbin’s paper again.  And it’s no secret there’s a fringe element that serve themselves.

Sadly enough, with all due respect to civil litigation lawyers, some are contributing to maintenance of the fringe solitude.

I attended the Expert Witness Forum East in Toronto in February and gave a talk on the principles governing cost control in civil litigation involving experts.  During a presentation by others I heard a lawyer suggest that experts should be retained on a contingency basis.  That suggestion has got to be out in left field considering that perception is everything in the judicial process.

The suggestion went nowhere in the ensuing discussion.  But the idea is out there and I’m sure there are fringe experts who will pick up on this idea and run with it and help maintain the “two solitudes” of expert services.

Fortunately, the judicial system is getting what it needs from the great majority of experts, whether it realizes it or not.  The fringe just muddy the waters a bit.  Still, the system has got to be on guard against the fringe experts scaling the bulwarks and taking over.  The fringe experts are out there.


  1. How experts are helping break the expert witness logjam.  Posted April 30, 2018 (A blog on Ruth Corbin’s  paper, following)
  2. Corbin, Ruth M., Chair, Corbin Partners Inc. and Adjunct Professor, Osgoode Hall School, Toronto, Breaking the Expert Evidence Logjam: Experts Weigh In, presented at Expert Witness Forum East, Toronto, February, 2018 (Google it)
  3. Are experts being being broadsided by bias, unbeknownst to them?  Posted April 12, 2018




Getting evidence in slip and fall accidents and building failures with video taken from a drone

I’m using drone-mounted cameras to get video of sites where people slip and fall and buildings fail.  The evidence is different, easy to get and cost effective – a few hundred dollars depending on location.  See Examples below also the References.

I take video almost exclusively because the resolution is so great in frame grabs that stills are not necessary.  Video is normally shot at 30 frames per second.  You can fly as fast or slow as you like, dip up and down, slip sideways and hover – videoing all the time.  Altitude and speed are recorded, and GPS on some drones.

There’s nothing technical about this.  You can get video with a simple, inexpensive camera fixed to a drone flying a few feet, 10s of feet or 100s of feet above and all around the site of an accident or failure.  The first aerial video I had taken was with a GoPro camera like those attached to a skier’s helmet for a scary run down a mountain.

Video from aloft is not the only means by which evidence is collected during a forensic engineering investigation.  This way, however, is relatively new, simple, cost effective and the evidence is from a different angle and sometimes quite revealing.  A DVD of the video on everyone’s laptop also enhances conference calls.

Following are some ways I’ve used video taken from a drone in recent years, or might have, and ways I may do in the future:

Example #1 Recently.What better way to survey and record defects in a high retaining wall involved in a flooding problem than from a few 10s of feet above the ground and off the face of the wall?  Example #2 Or identifying the potential location of fuel oil spilled on different properties as evident from distressed vegetation and colour changes in the ground so visible in a video taken from a few 10s of feet high?.

Example #3 A choice application would have been capturing the re-enactment of a nail gun accident on video from a few feet and right over the scene.  Unfortunately, there was no room for a drone to hover in the tiny room that was available – the actual scene was more expensive.

Example #4 My forensic investigation and re-enactment a few years ago of the John Morris Rankin accident at a test site at the Shearwater Airport would have been a perfect application of aerial video as would filming the 75 foot cliff over which John drove in Cape Breton.  As it was, I got good aerial video of the test site from a Sea King helicopter borrowed for the purpose.  I also got footage from the top of a rented boom truck.  Today I would use a drone fitted with a video camera.

Example #5 Quite recently I thought to use a drone to get video at a step-down and stumble accident site where there was lots of room to hover.

Example #6 Even more recently I’ve thought of using a drone to video the re-enactment of slip, trip and fall accidents in public places where I know there is lots of room to hover.  Places like auditoriums, sport’s facilities and airport terminals. 

You can grab frames at 1/30 second intervals from a video of a re-enactment and study slight changes in the movement of the slip and fall victim.

Techniques like these are being used now to estimate the speed of cars and airplanes in accidents.  Resolution is so good that you would be able to see the nail in a nail gun accident from 200 feet up – if there was an airport terminal with a ceiling that high.

There is also some chance that study of the condition of the floors as seen in the videos  - subtle changes in pattern, colour, texture, material or workmanship that contribute to floor skid resistance, – would cast light on the cause of the accidents.

This is like terrain analysis in civil engineering, – a well developed method – except indoors rather than outside.  The terrain’is a floor rather than the ground down hill of a fuel oil spill or along the proposed alignment of a highway.

Example #7  Also extremely valuable - surveying damage to the side of a multi-story building with a drone-mounted video camera – the former provincial land surveyor in me is enthused about this one.

Video could be taken from a distance of a few 10s of feet to document the character and extent of the damage to the wall, then from a few 10s of inches to measure the damage.  No expensive scaffolding necessary and workers climbing up and down.

Scale for measuring what is seen in the video would be got from the known size of building components used to construct the wall.  For example, the known size of a concrete block and the known thickness of the grout between concrete blocks

The character and configuration of the wall damage, and the size of cracks often points to the cause of the damage.  Random hairline cracks due to normal material shrinkage?  No worries.  Cracks that exhibit a predictable configuration and need to be grouted tell quite another story.  The cause is often almost a given, and would be one of the ways buildings fail.

Studies of how buildings fail have identified at least 209 different ways and they’ve all got causes. (Ref. 3)  And these don’t include all those involving the foundations and foundation soils – too often the Achilles’ heel of designers and builders.


This method – taking aerial video with drone-mounted cameras – is being used now in North America.   (It’s a new application of photogrammetry – the identification and measuring of the size of things on the earth as seen in photographs taken from the air)

Using video shot from a drone has got to be one of the most cost effective forensic engineering methods to develop in a long time.  Getting a lot of evidence quickly and cheaply is not too hard to take.

Like I said above, the savings continue when you distribute a DVD of the video to the parties involved for a conference call while each party views the scene on their laptop or device of choice.  I did this during one forensic investigation and surprisingly got more evidence still from comments made during our discussion.

With today’s technology, you can even ‘crew’ on a drone flight as ‘navigator’ by standing next to the ‘pilot’ flying the drone and direct the video to shoot from a remote display.  The video takes on more meaning when you’re part of the action.  I also end all my videos with footage of the pilot and myself, sometimes the plaintiff, standing on the site so there’s no question we were there.


  1. A picture’s worth a 1000 words, possibly many 1000s in forensic engineering with a new aerial photographic technique. Posted January 15, 2014 (see aerial photographs from a drone flight in this blog)
  2. New forensic aerial photographic method proving extremely valuable. Posted January 30, 2014
  3. How many ways can a building fail, and possibly result in civil litigation or an insurance claim? Posted July 10, 2014
  4. Forensic photography – the expertise available in eastern Canada. Posted February 26, 2015
  5. Fixed wing drones – another tool in forensic engineering investigation. Posted November 4, 2015
  6. “Crewing” on a forensic drone flight. Posted October 4, 2016
  7. Getting evidence with a low cost, low tech drone flight over a forensic site. Posted March 31, 2017
  8. Conference call on a “drone flight” reduces cost of civil litigation. Posted May 18, 2017
  9. “Unexpected” evidence and the importance of drone photography in forensic investigation. Posted July 19, 2017
  10. Drone video as a forensic technique is joined by drone photography as an art form. Posted August 2, 2017

Update: How I was tyrannized by the obvious during an engineering investigation

Who would have known that condensation was the real cause of the flooding in a furnace room – or so it seems now.  But don’t hold your breath at the rate this saga is unfolding.  Also note that forensic investigations can go off the rails like this too.

I blogged earlier (see below) on how I investigated the cause of flood water on a furnace room floor in a vet clinic and how I concluded it was obviously due to a high water table beneath the building.  Also how I was told later that it was really due to a burst water pipe in the washroom adjacent the furnace room after staff went there and saw water on the washroom floor.

The story could have ended there with me learning a valuable lesson, that if it seems obvious keep on investigating.  But it didn’t; my lesson continued a few days later.

Vet clinic staff called a plumber about the ‘burst pipe’, he came and investigated, saw the water on the washroom floor, looked for a burst pipe but found none.  He then looked in the washroom on the floor above.  Still no burst pipe but he did find water on the surface of the cold water pipes in the washroom.  The water was dripping on the floor and in turn on the washroom floor below next to the furnace room.

Water vapor in the moist washroom air had condensed on the cold water pipes.  This would be the same as vapor condensing on the inside of a window in the winter and water running down the window.  We’ve all seen that I’m sure.

So, the flood water in the furnace room was caused by condensation on cold water pipes, not by a burst pipe and not by a high water table.

To take inspiration from a quote by Hunter S. Thompson, “Wow! What a lesson!”. (Ref. 1)  I’ll keep you posted in the event there are more chapters in the saga.

You might ask, what’s this got to do with forensic engineering investigation?  It’s a reminder, that if being thorough in the investigation of water on a floor in a small room in an old building is important, it’s light years more important for the simplest of forensic investigations.


  1. Thompson, Hunter S., “Life is not a journey to the grave with the intention to arrive safely in a pretty and well preserved body: but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming “Wow! What a ride!”. (As cited recently at the celebration of a friend’s life)


Earlier Blog: How I was tyrannized by the obvious during an engineering investigation

It can happen to any of us, and it finally did to me.  I was tyrannized by the obvious when investigating the cause of flooding in a large, three story building.

A building renovator called me after water was seen on the furnace room floor by staff of a veterinary practice.  They had gone to the room where materials were stored and saw a few millimetres of water on the floor.  Not a lot but still.

The renovator said the building, which was erected in the 1960s, was on a concrete, ground-floor slab, on low land and near a lake.  The furnace room was enclosed by concrete block walls.  The flood water had pooled on the slab.  He estimated that the concrete floor slab was about five feet above the nearby lake surface.

When i went to examine the site I saw that the five feet was about right and that the furnace room was an estimated 50 feet from the lake shore.  I was also told that the lake level was higher than normal due to a lot of rain this spring.

The grounds around the building sloped down slightly to the lake shore.  The front and right side of the building were paved.  There was a lawn at the back and an old paved boat ramp on the left.  The surface of the boat ramp was bumpy after many years.

The corners of the furnace room were still wet where the concrete block walls rested on the concrete floor.

I had a good look around then walked across the floors of the different rooms in the practice.  They were a little uneven which wasn’t so unusual for an old building.  But my look around wasn’t as good as it might have been and I neglected to look in the small room adjacent the furnace room.

My examination complete I met with the owner and the renovator.  I noted how the water rises in a lake during frequent rain storms.  It also rises in dug wells.  The water in a well is the water table. The surface of the water table in the ground near a lake shore is usually higher than the lake.  There is also water in the soil above the water table due to capillary action – this is when water rises in the small voids in the soil above the water table (Check high school physics)

This higher water table plus some surface water runoff across the asphalt at the side of the building could explain the presence of the water in the furnace room.  It was obvious.  I mean, the building was so close to the lake with high water levels not seen in recent years and the furnace room floor was near the lake surface and the water table.

The irregular boat ramp was typical of frost heave due to water in the ground – a high water table and capillary action during wet springs over the years – and would back up this obvious conclusion further.

I talked about different ways of preventing water getting into the furnace room.  These included the obvious – terrible word – better perimeter footing drains and/or a sump pump.in the furnace room.  A sump pump is a pump in a depression or hole in the ground – a sump.

The sump pump was decided on as the least expensive and one that could be constructed several feet below the water table to draw it down below the furnace floor.  That decision was left with the building renovator.

I left the site after about an hour – an efficient examination and consultation, or a  hurried one?

A few hours later the renovator called to explain that a staff member had gone in the wash room – the one room I hadn’t gone in – adjacent the furnace room and found a burst water pipe, the real cause of the flood in the furnace room.

I was tyrannized by the obvious and guilty of expectation bias.  The moral of the story?  If it’s obvious, keep on truckin’ and do more investigation.