The nightmare of a late commission, a tight deadline, and writing an expert’s report in plain-English

I was surprised at how difficult it is to write a forensic report in plain-English for non-technical readers. It’s easy in technical-English but not so much in plain-English. Translating a foreign language – from technical to plain – is difficult.

Writing in technical-English just sails along because you’re reporting a thorough and objective investigation using words suited to the task, and there’s lots of guidance (Refs 1, 2 and 3):

  1. You identify each task – and many of these are standard tasks carried out in all forensic engineering investigations, including those when you follow-the-evidence,
  2. Describe the task,
  3. State why you did it,
  4. The data you got,
  5. Your analysis of the data,
  6. The light it shed on the cause of the failure or accident,
  7. Note how the findings of each task support, or otherwise, the findings on cause of other tasks, and,
  8. Finally, how the findings support your evolving hypothesis as to cause.

The investigation goes deep inside as you do your work. And then comes out easily when you sit down to write your report.

It’s easy to write technically because you’ve lived your investigation for days or weeks, and you’re writing for kindred souls, other technical people, in words that roll off your tongue. But, putting it in jargon-free, plain-English is another story.

A tight deadline makes writing in plain-English even more difficult. Like, you were retained months or years after the failure or accident, and the deadline is just around the corner. Nor when you get mini-briefings from your client as you write. The mini-data is good but it’s got to be analysed, checked against other data and included in the report – in plain-English.

I had all three during a forensic investigation a few months ago – late commission, tight deadline and mini-briefings. I also had non-technical readers so I decided to write in plain-English. That’s four.

I was reviewing my report weeks later after submitting it in preparation for trial and saw the odd phrase and word that I might have restated. No change in opinion just that the wording might be tweaked. I thought afterwards that I must write for the technical reader in late/early situations like this. Never mind plain-English. Too risky.

I also thought that all forensic reports should be written then put aside for a while and read again later before submitting. That’s how I draft my blogs, over a period of a good many days, or sometimes several weeks. It’s worked for blogging for nine years. It should work for forensic reports.

Forensic reports in plain-English for non-technical readers is a challenge for the writer but good for the client when you’re retained early and the deadline is way down the road. It’s bad, a nightmare, when the deadline is just around the corner.

I will continue to write my reports in plain-English but I’m alert to the difficulty – learned during the last few forensic reports I’ve written. One of these was submitted as a preliminary report because the deadline was so tight. I’ll write in plain-English because I enjoy reporting to the interface between engineering and other professions. This is also the reason I enjoy blogging on the nature and methods of forensic engineering investigation.


  1. Mangraviti, Jr., James J., Babitsky. Steven and Donovan, Nadine Nasser. How to Write an Expert Witness Report, 2nd ed., 2014, SEAK, Inc., Falmouth, MA (A massive 560 page, 1.25″ thick, 8.5″ x 11″ tomb)
  2. Zinsser, William K., On Writing Well, 7th ed., 2006, Harper Collins Publishers, New York (The best on the market for writing non-fiction. Note that it went to seven editions before the author died and sold 1.5 million copies)
  3. Nova Scotia Civil Procedure Rule 55 Governing Experts, 2010, and similar rules and codes elsewhere in the country (Hard-nosed guidance to ensure the expert reports all reasoning, including that possibly leading to a different opinion)

(Posted by Eric E. Jorden, M.Sc., P.Eng. Consulting Professional Engineer, Forensic Engineer, Geotechnology Ltd., Halifax, Nova Scotia, Canada June 11, 2021   

Why do I get real good forensic aerial video in the spring, fall and winter?

I’m learning all the time about new methods of forensic investigation.  And, for my readers, hopefully increased understanding of the nature of forensic engineering investigation.  For example, aerial video from a drone of a failure or accident in the built environment has been a real eye-opener for me and my clients in recent years. (Ref. 1)

It struck me recently while walking my dogs in a forest that spring and fall are good times for taking aerial video during a forensic investigation.  Winter too before the snow falls. On a sunny day you can see through the leafless trees to the brightly lit forest floor below.  I can see my dogs off at a distance in the leafless forest why not the forest floor from above?

Even as I draft this blog I’m learning.  It occurs to me that a cloudy day would be even better – no shadows to confuse what you’re seeing on the ground.

For example: I flew over a leafless forest in the spring during a road safety assessment that included a staged road accident for the first time and got excellent aerial video.  You could see a piece of gravel the size of a golf ball from 100 feet.  The video was a dispute-resolution maker.

To be upfront with you though, it was later seeing my dogs running in the leafless forest that made me realize why I got good aerial video during the road assessment.

Another example: I had another case, a fuel oil contaminated site, that was in a dense hardwood forest that was a prime candidate for this type of aerial video.  It didn’t come to pass – the case went off on another tack – but I was ready to capture good video through a leafless forest.

Aerial video of fuel oil contaminated sites in recent years has been a game-changer for me in treeless terrain – why not in leafless terrain too?

Why am I telling you this?  Because, if you’re processing a dispute or insurance claim that involves an accident or failure in the built environment, get aerial video of the site.  If there are leafless trees on or near the site, get aloft in a hurry.  COVID-19 is no problem because it’s easy to keep your distance outdoors.


Well, it finally happened to me early this spring, a deliberately planned aerial video of a site from a drone through a leafless forest. Plus some testing of forest floor visibility through the leafless trees. I couldn’t get on site fast enough.

And, as turned out, unexpectedly finding a surface feature that added to my understanding of the cause of a problem.

The aerial video was all part of the standard terrain analysis of a site during a forensic investigation. You identify the surface features characterizing the site and how these might shed light on the cause of the problem you’re investigating.

(Terrain analysis with aerial video is also used in basic engineering design and construction. For example, a firm I was with in Australia used terrain analysis to select the initial route of a road through a jungle in Indonesia)

Terrain analysis today involves:

  1. Checking Google Earth photography of the site,
  2. Studying stereo pairs of black and white and coloured aerial photography of the site – taken from 6,000 feet up, and all we had in the past, but still useful today,
  3. Looking at topographic and surficial geology maps of the site,
  4. Walking and visually examining the surface of the site – the boots-on-the-ground task,
  5. Taking eye-level photographs of the site, and, today,
  6. Getting and studying aerial video using a drone flying at altitudes up to 400 feet.

(A little aside. If nothing else, drone photography plus eye-level photography gives you that 3D view of your site. We didn’t have that prior to drone photography – only eye-level, 2D views. I’ve hired planes to get aerial photographs of a site in the past but that was expensive and not as effective)

I did all the bulleted tasks during my deliberate investigation this spring plus set out markers – sheets of white paper on the forest floor – to check visibility. Visibility was good through the leafless trees – no surprise. I also set out red traffic cones a measured distance apart to give scale to a drone photograph.

I studied the aerial video of my client’s site and discovered a feature off the site that contributed to the problem on the site. This feature was not visible during the boots-on-the-ground task.


It’s been an exciting two years as I discovered new ways of getting the most from aerial video taken from a drone:

  • Leafless aerial video,
  • 3D photography of a site,
  • Virtual aerial video of a site
  • Staged accidents to assess road safety, and,
  • Pre-planning aerial video with Fly Litchi app + Google Earth

I’m looking forward to summer like the rest of you, and I’ll get good aerial video of my sites, but I can’t wait for fall and winter and that leafless view.

Maybe I’ll let my dogs, Lily and Rosie, run free in the leafless forest during a drone flight. They deserve a treat for alerting me to why I get good aerial video in the shoulder seasons.


  1. A Bundle of Blogs: Aerial video of insurance and forensic sites taken with cameras mounted on drones. Posted October 31, 2019

(Posted by Eric E. Jorden, M.Sc., P.Eng. Consulting Professional Engineer, Forensic Engineer, Geotechnology Ltd., Halifax, Nova Scotia, Canada May 31, 2021   

Update: A Bundle of Blogs: On the need for peer review in forensic engineering and expert services

Expert reports are sometimes biased, particularly rebuttal reports. I found this out in a survey of seven experts in the Maritimes reported in the first of the following two blogs added to the Bundle.

The second blog in the following short list reports on six ways of getting rid of bias in expert reports.

There is a total of seven good reads in the updated Bundle of Blogs posted November 29, 2019.

  1. Is there an argument for a peer review of a peer review?  Posted January 11, 2020  I make the case for a peer review of a rebuttal report because most are biased.  I learned this after surveying the opinion of seven experts in the Maritimes. 
  2. Ridding peer review of potential bias.  Posted December 30, 2019  A good read on six different ways of getting rid of bias in a peer review, in decreasing order of preference. 

(Posted by Eric E. Jorden, M.Sc., P.Eng. Consulting Professional Engineer, Forensic Engineer, Geotechnology Ltd., Halifax, Nova Scotia, Canada. March 28, 2021   

How forensic experts can help fix old problems in dispute resolution

I was surprised and pleased recently to see the conclusion of a draft review article on how problems in the judicial process might be fixed. These are problems that result in delays in dispute resolution. The problems have existed for years and are caused by parties to a dispute arguing back and forth about the evidence in expert reports.

The article’s conclusion? Fix the problems by getting parties to:

  • Consider the “hot-tub” method of resolving differences in expert’s reports by experts agreeing a consolidated report (Ref. 1)
  • Alternatively, or together with, get reports prepared by experts according to codes like Civil Procedure Rule 55 in Nova Scotia, and the reports explained by experts in jargon-free talk

These are reports that assess the extent to which the data is:

  • Reliable – the extent to which an experiment, test, or measuring procedure yields the the same results on repeated trials
  • Valid – the quality of being well-grounded, sound, or correct like the validity of a theory
  • Relevant – relation to the matter at hand

To be fair, the fields of study giving rise to the issues in dispute haven’t seen a lot of hard science, and development of reliable investigative and assessment methods. The fields are empirical to some extent – based on observation or experience. Subjective rather than objective. As such, they are susceptible to unintentional misinterpretation, and also deliberately biased interpretation.

The issues arise in fields of study like medicine, the social sciences, soil mechanics and weather forecasting. Data and evidence from fields like these need to be gathered, analysed, interpreted and explained by scientific experts.

I know the science of soil mechanics is semi-empirical because I studied it in civil engineering. Its the study of soil as an engineering material – like steel, concrete and wood – and how it behaves when used in different ways. The safe support of the foundations of structures in the built environment relies on it’s principles.

I’m sure issues involving weather forecasting could cause trouble too.

It’s easy to imagine difficulty with issues involving the social sciences. These sciences describe, measure and study people’s beliefs, behaviours, experiences, perceptions, and what they do or intend to do in their communities. They often rely on statistical studies that don’t always have wide acceptance, partly because of the potential for bias. They are not hard-nosed like the engineering investigations of problems in the built environment.

The review article suggested that the problems in these softer, semi-empirical fields of study might be reduced if an expert’s report was written according to Code and the report explained by an expert in simple terms. Or, where this approach is accepted and practiced, consider getting experts to confer and agree a single report – the hot-tub method.

The draft article was a delight to read. I can’t wait to see it published.


  1. “Hot-tubbing” experts reduce cost of civil litigation and ensure objectivity. Posted March 31, 2018

(Posted by Eric E. Jorden, M.Sc., P.Eng. Consulting Professional Engineer, Forensic Engineer, Geotechnology Ltd., Halifax, Nova Scotia, Canada, April 16, 2021   

Getting that festive feeling when evidence “pops out at you” during a forensic investigation

I enjoyed seeing the article in last Saturday’s paper about using the remote images from aerial and mapping techniques to investigate archeological sites – techniques like Google Earth, LIDAR and old maps. (Ref. 1) The images from these methods have existed for a while but are now being combined in new ways. I’ve used the images separately in the forensic investigation of failures and accidents in the built environment.

The article is a good, informative, almost jargon-free read that might herald what’s coming in forensic investigation.

The difference today is that an archeologist, Dr. Jonathan Fowler, Saint Mary’s University, Halifax is using software to combine the remote images from different methods to get a 3D view and even more data from a site. Data “pops out at you” to use Dr. Fowler’s expression. The software is produced by Golden Software in Colorado.

Example of Dr. Fowler’s work

A good example in the article of Jonathan’s work is certain to interest you. It shows different remote images of historic Fort Anne and Fortress Louisbourg in Nova Scotia.

The images are remote because they’re from cameras and sensing devices that are high above a site – a little like the images from video cameras mounted on drones that are flying low over a site.

Jonathan’s recent work has been made possible by the Nova Scotia government releasing in 2020 great volumes of free LIDAR data; “…it just felt like Christmas to me.” (Ref. 1) The data is available to the man-in-the-street for most of Nova Scotia.

Examples of forensic work using remote images

#1 I had that festive feeling when the government gave me LIDAR imagery for the site of a swimming pool failure in Cape Breton several years ago. I was investigating the reason one end of the swimming pool was several inches lower than the other. You could see the difference in the distance from the pool deck to the water’s surface. The cause popped out from the imagery: The swimming pool was built on filled ground over a bog – compressible foundation soils in the extreme.

#2 A few months ago Google Earth imagery enabled me to virtually visually assess the cause of a retaining wall failure in Ottawa and contribute to a big reduction in the cost of the wall’s rebuilding.

#3 Free software that relies on Google Earth imagery enables me to plan video of the site of a failure or accident from a virtual drone flight over the site days before and hours of driving away. This has been a godsend for me in my forensic work – a more effective investigation at lower cost.

#4 In the past we used what are old maps today: Large scale, contoured, topographic maps of built up areas made from aerial photographs taken from planes flying at 6,000 feet. They can be quite detailed and accurate. We would be remiss not to refer to them today, and couple them with Google Earth and LIDAR imagery like Jonathan is doing. Even older maps exist today of sites like Fort Anne and Fortress Louisbourg.

#5 I’ve also used stereo pairs of aerial photographs to assess the terrain at a forensic site – terrain analysis in engineering. Details of micro-topography revealed in an analysis often give evidence of features below the surface. (Ref. 1) It was a standard technique in an Australian firm where I worked when selecting a route for a highway in a remote area of Indonesia.


It just keeps getting better what archeologists and forensic engineers can get today from remote imagery and suitable software.

Still, ground proofing is needed – getting your hands dirty and mud on your boots walking around on the site. This to confirm what you thought you saw in the pictures and images from above. It’s an old technique and a hard and fast rule in engineering, as I’m certain too in archeology.


(LIDAR, or Light Detection and Ranging, uses pulsed laser to measure the earth’s surface)


  1. Archeologist Lauds Advances in Mapping, Peddle, Stuart, The Chronicle Herald, Halifax March 27, 2021

(Posted by Eric E. Jorden, M.Sc., P.Eng. Consulting Professional Engineer, Forensic Engineer, Geotechnology Ltd., Halifax, Nova Scotia, Canada, March 31, 2021   

Principles governing the cost control of dispute resolution and claim settlement involving experts: Update

It’s a given that we must do sufficient forensic investigation to resolve the dispute or settle the claim. Sometimes that can be as little as a low cost virtual visual site assessment. (Refs 1, 2) Particularly, if the direction that the investigation seems to be heading is sufficient for the parties involved. A detailed investigation is not always necessary.

I thought, this low cost method, a virtual visual site assessment, must be reflected in the Principles. (Ref. 3) It fits in well with the different ways an expert can be retained (Ref. 4) as commented on in Principle 5 in the Principles.

This method came to mind several times in the last few months after COVID-19 hit. It also reflects the intent of the rules governing experts brought in a few years ago – to work disputes out and stay out of court, (Civil Procedure Rule 55 in Nova Scotia), and I imagine even avoid the expense of Alternate Dispute Resolution (ADR).

I’ve updated the Principles by revising the Comment on Principle #5. You can see the updated Principles governing the cost control of dispute resolution and claim settlement involving experts. Posted July 30, 2019 by scrolling to the July date at


  1. What can you get from virtual visual site assessment about the cause of a leaning retaining wall? Posted November 13, 2020
  2. A Bundle of Blogs: On using visual site assessment in forensic investigation. Posted January 25, 2021
  3. Principles governing the cost control of dispute resolution and claim settlement involving experts. Posted July 30, 2019
  4. How to retain an expert in a cost effective way. Posted November 30, 2018

(Posted by Eric E. Jorden, M.Sc., P.Eng. Consulting Professional Engineer, Forensic Engineer, Geotechnology Ltd., Halifax, Nova Scotia, Canada March 18, 2021   

Why am I feeling good about blogging these days?

The reason has everything to do with cost effective, quite reliable forensic investigation. I’m realizing, more and more, how easy this can be.

People still get hurt and things break and fall down during a pandemic and someone wants to know why – like injured parties, lawyers and insurers. At least well enough to resolve a dispute or claim in some fashion.

Well enough doesn’t mean exhaustively, at least in the beginning, nor necessarily at all.

This acceptance of well enough has coincided with my interest lately in how much forensic investigation is enough. It also suits the requirement these days to stay home/in-the-office and minimize social and work contact.

My interest developed on realizing experts often know the cause of an accident or failure with considerable certainty very early in an investigation. (Ref. 1) And well enough to resolve a dispute or claim.

Experts know this based on their experience and the well known causes of so many problems in the natural and built environments. (Ref. 2) And also knowing the many parameters that could be investigated in slip, trip and fall accidents, and going about this efficiently. (Ref. 3) The parties to a dispute see where an expert’s findings might go and decide to resolve rather than spend more money.

I’ve been blogging on these aspects of forensic investigation for some time in the interest of more cost-effective work. This also suits pandemic times just fine.

My interest was kick-started

  • When I realized the value of drone photography in recent years, (Ref. 4)
  • Moved along when I researched the different ways structures can fail and these classified and used in forensic investigation, (Ref. 5)
  • Went faster in the last year or so on recognizing the need and value of virtual visual site assessments during COVID-19, (Ref. 6)
  • And faster still when I realized the reliability of virtual assessments could be subjectively and usefully quantified, (Ref. 7)
  • Jumped forward on assessing the cause of a retaining wall failure in Ottawa based on a virtual visual site assessment, (Ref. 8)
  • Took off during that retaining wall assessment on seeing the contribution of Google Earth Pro photography to my assessment of the wall, (Refs 9 and 10)
  • Was reinforced when I got word back on how my virtual visual site assessment of the retaining wall contributed, along with input by others, to reducing the re-construction costs of the wall by almost half, and
  • My interest finalized on realizing how forensic investigation of the dozens of parameters that need to be considered in slip, trip and fall accidents can be dealt with efficiently and cost effectively with a simple initial task and many parameters eliminated, (Ref. 11)
  • But, just to be sure, add in 3D plotting of the results of a slip and fall investigation using an app and Google Earth Pro. (Ref. 9)
  • If that’s not enough, my interest was driven home on realizing how Zoom meetings will add further to cost-effective forensic engineering investigation.

This is the reason I’m blogging these days. It’s hard not to. It’s exciting and very satisfying to see quite reliable, cost effective forensic investigation in dispute resolution.

At the end of the day, this reason reflects the purpose of my blog: To explain the nature and methods of forensic engineering and expert services in jargon-free writing to non-technical people like civil litigation lawyers, litigants, injured parties, insurers and property owners.


You might also take a look at the blogs posted on August 15, 2019, July 13, 2018, June 30, 2017 July 22, 2016 and August 7, 2014 about my reasons for blogging, particularly the first in this list: August 15, 2019; a good read.


  1. You could be excused for thinking that everything is falling down. Posted July 23, 2020
  2. What’s in “…the built environment” and how many ways can it fail? Posted July 8, 2020
  3. Experts, Litigants, Insurers: Beware! There are dozens of parameters that could be investigated at slip, trip and fall sites. Posted February 18, 2021
  4. Drone photography continues to soar to new uses in forensic investigation. Posted March 30, 2020
  5. What’s in “…the built environment” and how many ways can it fail? July 8, 2020
  6. A Bundle of Blogs: On using visual site assessment in forensic investigation. Posted January 25, 2021
  7. The reliability of an educated guess on the cause of a failure or accident. Posted October 22, 2020
  8. What can you get from a virtual visual site assessment about the cause of a leaning retaining wall? Posted November 13, 2020
  9. Using Google Earth photographs in forensic engineering investigation. Posted December 5, 2020
  10. A Bundle of Blogs: Aerial video of insurance and forensic sites taken with cameras mounted on drones. Posted October 31, 2019
  11. What does an engineering expert do at the scene of slip, trip and fall accidents? Posted February 5, 2021


(Posted by Eric E. Jorden, M.Sc., P.Eng. Consulting Professional Engineer, Forensic Engineer, Geotechnology Ltd., Halifax, Nova Scotia, Canada February 26, 2021      

Experts, Litigants, Insurers: Beware! There are dozens of parameters that could be investigated at slip, trip and fall sites

I was prompted in a recent blog to recommend assessing the physical setting of a site first then go to more detailed investigation later, if necessary. (Ref. 1) This cost effective, staged approach works in other fields of engineering investigation, why not for slip, trip and fall accidents?

Use the data gained to identify in a second stage the most important components of the accident and how they relate. Then in a third stage focus the investigation on the parameters characterizing these components, rather than on the many dozens. This approach is reliable and cost effective.


I was struck again on leafing through the literature on the many factors that could be investigated. I thought, I must make sure readers understand the cost effectiveness of this approach.

One exhaustive European study of the slip resistance of footwear has also been accepted by American firms that design, manufacturer and sell skid testing equipment. (Ref. 2) The study counted the following approximate numbers of parameters/factors for the four main components of an accident that would need to be investigated:

  1. Floor covering component: … 34 parameters
  2. Lubricant: …………………………….. 28
  3. Shoe: ……………………………………… 23
  4. Ambient parameters: …………. 22

Other researchers identified more components and fewer parameters but this gives you an idea of the possible magnitude of forensic investigations of slip, trip and fall accidents.

For example, take the shoe component from the above list. The 23 factors can be grouped under:

  1. Type of shoe
  2. Properties of the shoe material, and,
  3. Design of the tread

An investigation of the Type of shoe would determine if the accident victim was wearing a leisure shoe or a work shoe/boot, or if the victim was barefoot.

Investigation of the Properties of the shoe material might look at the type of material, the additives present, the hardness, density, elasticity and strength of the shoe material, whether it was a single or dual layer sole and it’s chemical composition.

Investigating Design of the tread would determine the size and width of the shoe, the geometry and depth of the tread, it’s texture, it’s roughness, the edge finish, the amount of wear and if there were cleats.

This involves a lot of forensic engineering investigation – just of the 23 parameters in the shoe component.

Then add in all the factors associated with the Floor covering – as many as 34 depending on how you count them. And any Lubricants present, about 28 – like rain water in a foyer and cooking oil in a kitchen. And the 22 Ambient parameters, including weather and temperature, the many human factors, the floor gradient and lighting, and the existence or absence of handrails.

This could add up to an exhaustive engineering investigation – if its not done right – and a red light for both experts, litigants and insurers Beware!

This has come out of one widely accepted study in Europe that is accepted in the U.S. And no question in Canada. I’ve read and seen how other American studies tweak the European work and add a little more to a forensic investigation.


For sure, some of the many factors I’ve noted above would be covered off quickly after the physical setting of the accident site has been surveyed.

For example, was the victim wearing a recreational shoe or a work boot? Was it raining that day just outside the foyer? Was the victim walking or running? Were there handrails on the stairs, and did the ratio of step width to riser conform to the standard of practice for stair design?


I believe, considering the dozens of factors involved, (Ref. 2) – and hopefully you have a better understanding of this from the above – that slip, trip and fall accidents are prime candidates for peer review of the expert’s forensic investigation. (Refs 3, 4 and 5) Particularly if the investigation involves additional stages after initially assessing the physical setting of the accident site. (Ref. 1) Peer review is cast-in-stone in science and should be in the investigation of slip, trip and fall accidents.


  1. What does an engineering expert do at the scene of slip, trip and fall accidents? Posted February 5, 2021
  2. Sebald, Jens, System oriented concept for testing and assessment of the slip resistance of safety, protective and occupational footwear, Pro Business Gmbh, Berlin 2009
  3. Is there an argument for a peer review of a peer review? Posted January 11, 2020. A good read.
  4. Ridding peer review of potential bias. Posted December 30, 2019. Another good read.
  5. A Bundle of Blogs: On the need for peer review in forensic engineering and expert services. Posted November 29, 2019

(Posted by Eric E. Jorden, M.Sc., P.Eng. Consulting Professional Engineer, Forensic Engineer, Geotechnology Ltd., Halifax, Nova Scotia, Canada February 18, 2021   

What does an engineering expert do at the scene of slip, trip and fall accidents?

In the beginning, to ensure a reliable, cost effective investigation, s/he should do no more than capture the physical scene where the accident happened – and do this quickly before conditions change.

An expert does this by carrying out as many as 13 different tasks at or near the specific location of the accident indoors or outdoors.

For example, if the accident occurred indoors:

  1. Video and photograph the site as seen by the victim and as seen from a drone,
  2. Measure the slope of floors and ramps, and the width and rise of stairs
  3. Record the nature and surface condition of the materials forming these features,
  4. Measure the location and construction of handrails and guardrails,
  5. Record the presence of debris, liquids or dust at the location of the slip, trip or fall accident, and,
  6. If the shoe or boot is available, examine and record it’s construction

Carrying out these tasks and others is basically an elaborate visual site assessment. Nor is it unlike a topographic survey outdoors that might be done by a provincial land surveyor.

Use the data from this work to show the scene in accurate drawings and photographs. Make, what we call in engineering, as-built or as-constructed drawings. These can also be rendered today with the software that is available in very impressive 2D and 3D formats.

Components of accidents

The expert should refrain initially doing more because these types of accidents have several components. The relevance of each of these to one another and to the accident can’t be evaluated – and the significant one(s) focused on – till the physical setting is nailed down. Trying to do otherwise is expensive – a waste of time and money.

A list of the components of the slipping- or tripping-while-walking hazard looks like the following: (Refs 1, 2 and 3)

  1. Person
  2. Activity
  3. Floor covering (walking or working surface)
  4. Lubricant
  5. Footwear (slider)
  6. Ambient and environment parameters

Each component contains a lot of parameters that are far too numerous to list here. A few are noted in the following:

The condition of the person involved can be crucial. For instance, gender, age, experience and personal situation help determine how much caution a person uses.

Some activities require more foot traction than others. For instance, walking normally in a straight line is least demanding. Walking fast, turning or stopping is more risky.

The floor covering is likely to be different for walking surfaces compared to working. The properties of the floor are important in traction. These are determined by no less than two and half dozen parameters.

A lubricant can be any substance between the walkway and the footwear that reduces slip resistance. Water is just one. And it can get on the floor in different ways both inside and out. For instance, at drinking fountains and sinks indoors and by lawn sprinklers outdoors.

An accident occurs when there’s insufficient traction between footwear and the walking or working surface. A couple of dozen properties characterize the contact between the footwear and the floor in determining traction. Material properties and tread are of paramount importance.

(Ice cleats on boots won’t necessarily save you. I found this out this morning while cleaning wet snow from the timber stairs up to my deck. I slipped on the stairs but can run on ice with these cleated boots. So why the slip? February 2, 2021)

For sure, the environment influences the slipping-while-walking-hazard. Parameters like weather in general – sunshine, rain, snow, wind and humidity. But also lighting, surface slope, handrails, and room equipment and furniture.


The engineering and scientific literature has identified numerous factors in the slip, trip and fall hazard. (Refs 1, 2 and 3) Legal and claim settlement practice manuals have identified others relevant to resolving disputes arising from these accidents. (Ref. 4)

The engineering expert must focus on the big picture initially – the setting of the accident – and do this quickly. And in the process identify the relevant components and parameters for more detailed investigation. This is the only way forward in reliably and cost-effectively determining the cause of slip, trip and fall accidents.


  1. Sebald, Jens, System oriented concept for testing and assessment of the slip resistance of safety, protective and occupational footwear, Pro Business Gmbh, Berlin 2009
  2. Sotter, George, P.E., Ph.D., Stop Slip and Fall Accidents!, Sotter Engineering Corporation, California, 2014
  3. Di Pilla, Steven, Slip, Trip and Fall Prevention, A Practical Handbook, 2nd edition 2010 ESIS, Inc. CRC Press, Boca Raton
  4. Turnbow E, Charles, Slip and Fall Practice 2nd edition, Revision 17 2012 James Publishing, Inc.

(Posted by Eric E. Jorden, M.Sc., P.Eng. Consulting Professional Engineer, Forensic Engineer, Geotechnology Ltd., Halifax, Nova Scotia, Canada February 5, 2021   

A Bundle of Blogs: On using visual site assessment in forensic investigation

A visual site assessment – including a virtual visual site assessment – is a valuable task in the investigation of a personal injury or failure. This is obvious in the following blogs that I have posted in the past. This type of assessment is particularly valuable during a pandemic.

In a real assessment, the forensic expert (1) gets briefed (2) reads the documents (3) studies existing photographs and drawings, then (4) goes to the site of a personal injury or a failure, (5) examines the exposed surfaces at the site, (6) notes what’s there and what’s not, (7) takes some measurements and (8) additional photographs, (9) gets stills from Google Earth Pro and (10) perhaps video from a drone.

S/he does not (1) look below the surface, (2) take things apart, (3) do intrusive field testing, or (4) laboratory testing. These tasks come later if required.

A lot of data and evidence is gathered this way, sometimes enough to reason to a conclusion and form an opinion on cause sufficient to resolve a dispute or settle a claim.

A virtual assessment – sans site visit and the expert getting his hands dirty and mud on his boots – is also good, and sometimes enough. If it has a shortcoming, the expert doesn’t get “calibrated” to the site as well as he might.

I’ve done several virtual assessments, one a few months ago at the site of a trip and fall. Others of a retaining wall, bridge and building collapses, and a trench cave-in.

Fortunately no lives were lost during the cave-in but an oil tank was taken down. I investigated and reported on the cause after doing your standard virtual visual site assessment (see steps above). My client requested that I not visit the site, not even to drive the nearby roads.

One assessment resolved an 11 year dispute after a four month forensic investigation. A person was injured by ice falling off a structure. In hindsight, that investigation was half real and half virtual – I examined the exposed surfaces with binoculars from a distance.

Interestingly, I got some insight into the formation and risk of ice on structures while coming and going from a ski lodge at Mont Comi on the Gaspe Peninsula. Also seeing ice on buildings during a visit to my daughter’s horse farm in Maine. Forensic engineers work even when they’re playing.


In the following, I’ve listed a few recent blogs on real and virtual visual site assessments that are particularly relevant in COVID-19 times. I’ve posted others in the last 8.5 years but the following are enough.

At the end of the day, while a visual site assessment, whether real or virtual, is often enough for a dispute or claim, it’s not always. Intrusive field work and an in-depth examination of the site is invaluable. “Calibration” of the expert is also valuable.

The Bundle of Blogs on Visual Site Assessment – Real and Visual

  1. COVID-19 and forensic engineering investigation. Posted May 7, 2020 It struck me one morning while walking my dogs that forensic engineering investigation is not prevented by COVID-19.  Experts often work alone as principal investigators conferring with other specialists as needed.  Many of the most experienced experts are sole practitioners.  We already “work from home” in a sense and have for years.
  2. COVID-19 and an initial forensic task a.k.a. a visual site assessment, sans social distancing. Posted June 1, 2020 This blog reminds us that the visual site assessment is carried out by a lonely expert whether for real on site or virtually. Social distancing is not an issue. It also reminds us that it’s an essential task that should be done before the dust settles at the site of a failure or accident.
  3. Get on site and do a forensic visual assessment before COVID-19 returns. Posted September 10, 2020 This seems a bit of a joke this day as the second wave of the pandemic continues to wash over us. But the blog does contain nice comment on how document review, virtual site assessment and on-scene assessments work together to yield a lot of data and evidence on the cause of a failure or accident.
  4. Why did the four story building collapse during construction in London, Ontario. Posted December 31, 2020 I examined the construction site virtually as evident in news photographs and comments by workers. My engineering experience on multi-story building construction identified the probable cause quite quickly. (It’s interesting that two other experienced engineers came up with the same answer, based on virtual visual site examination)
  5. What can you get from a virtual visual examination about the cause of a leaning retaining wall? Posted November 13, 2020 One thing was contributing to a significant reduction in re-construction costs – up to one half! My contribution was based on study of 26 photographs, video from a drone and screen grabs from Google Earth Pro video. I got a lot of data on why the wall was leaning. To be truthful, I could not have done too much better if I had been able to go to the site and do a real visual examination rather than the virtual. This was one of the most satisfying virtual visual site assessments I done.
  6. What can you get from a virtual visual examination of an accident scene. Posted August 28, 2020 I was contacted and sent two photographs of where a person fell and was injured at the entrance to a building. Virtual examination and virtual measuring of the entrance identified contributing factors in the accident. They were so obvious.
  7. Wind, construction crane and inadequate cross-bracing caused Edmonton bridge failure: An initial hypothesis. Posted March 27, 2015 This was one of the most exhaustive virtual visual examinations and data analysis that I’ve done. I also chatted with three structural engineers for insight to add to my own understanding of bridge design and construction. The behaviour of a construction crane in strong winds caused the failure.
  8. Counsel: Your case benefits when you visit the scene of a personal injury accident or engineering failure. Posted April 30, 2016 In a sense, this was a visual site assessment by counsel in a slip and fall case that paid dividends for counsel. He went to the accident site to watch me carry out skid resistance tests. Later management cancelled further expert work including submission of a report on the skid testing. All that counsel had to argue his case was his viewing of what took place – his personal visual site assessment – and my verbal comment on the results as we drove back to the city.
  9. Can you “calibrate” a forensic expert? Posted June 23, 2020 This is a good read, a bit of an eye opener as to what happens to an expert when s/he goes to a site and collects hard data. An expert does get “calibrated” to the scene of an failure or accident during a visual assessment. The process also happens to some extent during a virtual assessment.

Related to the Blogs in the Bundle

  1. Where does an expert’s initial hypothesis come from? Posted February 25, 2019. Updated March 18, 2019 This is a another good read on how we process the data that we get from a real or virtual visual site assessment.
  2. The reliability of an educated guess on the cause of a failure or accident. Posted October 22, 2020. This is a blog we should read on how the reliability of an expert’s opinion might be quantified – at least made less subjective.

(Posted by Eric E. Jorden, M.Sc., P.Eng. Consulting Professional Engineer, Forensic Engineer, Geotechnology Ltd., Halifax, Nova Scotia, Canada