Counsel: Your case benefits when you visit the scene of a personal injury accident or engineering failure

It’s better still when you watch the forensic engineer do some of his work.  We learn by seeing and doing – something like 80% to 85% of what we know is got visually.  At the very least, you will better understand your expert’s explanation of the cause of the accident or failure.

I was reminded of this recently when a client indicated that he got a lot sitting and watching me work.  I think he was quite taken by what he saw and I was impressed that he wanted to go to the scene with me.  He resolved his case based in part on what he experienced that day and the pictures he took.  I wasn’t required to give even a verbal report let alone a written report.

I was also reminded of the benefit of a site visit when I met and spoke with a forensic photographer recently – photographs, the next best thing to being there, and also good for refreshing your memory of a site visit – and when I read a short manual on forensic photography. (Ref. I)

Counsel, we don’t see you at the scene very often.  I can think of only four times in recent years.  Engineers swear by the worth of a visual assessment of a site. (Refs 2 to 6)  You are also certain to get a lot from going to the scene.

What does Counsel see when s/he goes on site?  Aside from picking up a valuable concrete impression of the scene of the accident or failure?

1. Slip and Fall Accident  Counsel and the injured party sat and watched me use non-textbook methods to investigate the cause of a slip and fall accident.  I tested the skid resistance of the floor using pork belly – a pig’s belly skin, to simulate the injured party’s bare feet.  This was recommended by medical doctors and veterinarians.

There was also a question about the source of water on a floor that was supposed to be dry.  I thought earlier about a shower in a dressing room but it was some distance away.  Still, maybe.  So I put my bathing suit on that I had with me, took a shower and walked to the area of the fall – dripping water along the way and on the “dry” area.

My client got an eye-full during his site visit.

2. Inadequate Underpinning  A young lawyer watched me excavate and expose the underpinning of a building using a backhoe and manual labour – me doing the manual work, during three days of investigative site work.  She also watched me examine the underpinning closely, and measure and photograph it.  Real dirty hands and muddy boot work.

I tried to get her down into the muddy excavation to see up close one of the worst deficiencies of the inadequate underpinning but that was too much for her.  Still she saw it from the edge of the excavation and reported back to her manager.  I’m certain she will remember that site experience and be guided by it if she practices civil litigation.

Her manager was to be commended sending her to the site.  It would have been much better if he had got out there – the one arguing the case, but at least someone did.

3. Foundation Failure  The owner’s lawyer held meetings in an industrial building that was supported on foundations that were still settling and damaging the building 10 years after construction.  He saw the building and the cracks in the walls up close.  He got visual impressions that helped him understand the report I wrote on the extent and cause of problem.

Unfortunately he was not there when I strengthened the foundation soils by grouting – a ground improvement technique not often seen in Atlantic Canada.

4.  Flooding  Counsel came to the site and saw the flooded land and the unusual source of some of the flood water.  I later took low level, oblique aerial photographs with a camera mounted on a drone – the first time I used this technique, and gave them to the lawyer to refresh his memory of what he saw when he was on site.  He didn’t say but I know it benefited him.  Hard not to.


I’m certain the lawyers in these cases understood my explanation of the technical issues much better after being on site, and also argued their cases more effectively.

It’s not a substitute for Counsel visiting the scene of an accident or failure but low level aerial photographs are making the expert’s job of informing the justice system much easier.  They’re that good.

They could also entice Counsel to go to the scene more often, see for himself and get a little mud on his boots if not dirt on his hands.  The young lawyer above – standing at the edge of the excavation, got the former but not the latter.  Nevertheless, she benefited just being there.


  1. Matthews, Kenneth M., Pink, Joel E., Tupper, Allison D., and Wells, Alvin E., The Expert, a Practitioner’s Guide, Chapter 15 (by Tupper, Allison D) Use of Forensic Photographs at Trial and Chapter 15A Use of Photographs and Photographic Interpretation, an example – R. v. McGillivray Carswell Publishing 1995
  2. “Technical” visual site assessments: Valuable, low cost, forensic engineering method.  Posted September 4, 2012
  3. An expert’s “dirty hands and muddy boots”.  Posted December 20, 2013
  4. The messiness of some forensic engineering and insurance investigations is illustrated by messy snow banks.   Posted April 14, 2015
  5. More about messy, lumpy Mother Nature and how we deal with her effect on our forensic engineering and insurance investigations.  Posted April 23, 2015
  6. The justice system and messy construction sites – Seeing is believing.  Posted December 17, 2015



Legal causation in bodily injury: Forensic engineer’s view

A plaintiff’s lawyer doesn’t have a reliable legal claim – and money well spent on a medical expert, until the technical issues in a personal injury case are identified and investigated, and the cause of the accident established.  Only then can the responsible parties be reliably identified by the lawyer.

I know this because I have been retained as an expert to investigate the cause of accidents like slip and fall, motor vehicle, toxic fume emission and ladder falls.  There are different elements in cases like these.  Legal and medical elements are two.  The technical element is another – an important one that comes first in a personal injury case if it’s to start off on the right foot.

There are also several different involved parties depending on the technical cause of the accident – at least four in a slip and fall accident. (Refs 1, 2)  And a similar number in a ladder accident.

I was reminded of this when I read about the plaintiff legal practice conference entitled “The Doctor Is In: Medical Elements of Injury Cases”.  It’s planned for this June in St. John’s by the Atlantic Provinces Trial Lawyers Association (APTLA).

The two day conference looks extremely good for practicing lawyers with at least a dozen featured topics and national and international speakers from the medical and legal professions. The topics are medical or closely related as would be expected.  The topics on the law of expert evidence and preparing to discover an expert are also timely, particularly to those of us retained as experts.

An important two-part topic is on causation:

  1. A pathologist’s view of medical causation in bodily injury
  2. Legal causation, the law and variance from medical causation

This topic really needs to be treated in three parts for an even more complete and comprehensive conference:

  1. A pathologist’s view of medical causation in bodily injury
  2. Legal causation, the law and variance from medical causation
  3. A forensic engineer’s view of technical causation in bodily injury and how it varies from legal causation

How can a lawyer confidently and reliably process a plaintiff’s claim for damages arising from bodily injury when he or she doesn’t know the technical cause of the accident and from that the party(s) responsible?  The emphasis is on confidently and reliably because lawyers are doing it now and managing often enough.  But that’s not good enough.

Establishing causation involves a two-stage inquiry: (Ref. 3)

  1. The first stage involves establishing ‘factual’ causation.  That is, determining exactly what happened and who might have been involved in the incident.  This is the forensic engineering investigation.
  2. The second stage involves establishing ‘legal’ causation.  This is when a lawyer reviews the factual causation – after it’s been established, and determines if the law is involved in the incident.

Determining factual causation in cases like the following is not lawyer-work.  It’s not even in the engineering text books in some cases and for certain not in the medical and legal text books.  A forensic engineer often has to “figure it out” as he goes along.

And often enough there is more than one party involved in what happened.  These parties are not known until the engineering investigation is complete.  I’ve seen the wrong party named in cases that were filed months, sometimes years before I was retained to investigate an incident.

Some examples of personal injury cases:

  • I used a piece of pork belly – a pig’s belly skin, to investigate one slip and fall accident,
  • also showered and walked across an accident site dripping water from my bathing suit to learn where water on a floor came from,
  • investigated soap detergent on a stair landing at a retail outlet,
  • carried out full scale field tests in a fatal motor vehicle accident,
  • planned full scale tests using a Hollywood-style stunt man in a fatal step ladder accident,
  • researched how a building “breaths” in one toxic fumes emission case and
  • how fuel oil weathers in the ground in another, and,
  • used binoculars to establish the cause of a man’s head injury from falling ice.
  • a colleague investigated a trip and fall accident where the injured party was half-running backwards

Cases like these don’t get resolved until the technical issues are identified and investigated.  One of the above cases went on for 11 years then settled in 4 months after I completed my engineering investigation and established cause.  Many months to a few years is normal.  For sure, some of the delay is due to short comings and backlog in the justice system but not all.

I’ve seen similar situations in cases involving structural deficiencies and engineering failures and collapse in the built and natural environments as distinct from personal injury accidents.

Until the technical issues are identified and investigated thoroughly, technical causation established and the involved parties identified, the doctor’s view of medical causation might suffer for lack of some technical data.

And the practicing plaintiff lawyer won’t know who to sue, confidently and reliably – he could well be out on a limb.  To borrow and modify a comment in the description of the conference topics, “Don’t let (missing data on technical) causation sink your case”.

A three-part topic on causation is needed at the conference in St. John’s in June – medical, legal and technical – if the APTLA membership and their plaintiffs are to be even better served.


  1. Sebald, Jens, Phd, System Oriented Concept for Testing and Assessment of the Slip Resistance of Safety, Protective and Occupational Footwear, Pro Business Gmbh, Berlin, 2009
  2. Di Pilla Steven, Slip, Trip, and Fall Prevention, a Practical Handbook, 2nd ed., CRC Press, New York, 2010
  3. Wikipedia, April 12, 2016




Thinking about the cause of “wavey”, sagging floors in a building and how Counsel benefits

I recently mentioned how you can think – hypothesize, about the cause of a failure or accident based on very little evidence, then modify your thoughts as more comes in. (Ref. 1)  This is the nature and technique of forensic engineering investigation.  Some of the evidence can be as brief as a chance remark years ago, as happened to me.  Following is another example of this process.

(Counsel benefits from a process like this – ideally when the merits of the case are assessed.  But also when you think you have enough technical evidence to go forward and want to cut costs by stopping the forensic investigation)


There are a lot of multistory buildings in the Halifax area.  I learned that at least one is defective because the floors are sagging – the floors are “wavey” to use one person’s description.  A defect is a failure in engineering.

The floor in one of the rooms on the 10th floor slopes down 1.5% to 2.5% from the end to the middle.  It sags in the middle.  The room is 22 feet long by 12 feet wide.  That means the floor sags 2 to 3 inches.  That’s a lot for a commercial building.  It’s far more than a construction tolerance of 1/4 inch.  You can see the slope in the length of the conference tables.  I measured the floor with a tape and a digital level.

In another large, square room chairs with casters roll to the left side of the room when you’re sitting in one.  That happened to me.  The floor slopes down to the left in this room compared to the middle in the other room.  At least on the left half of the room where I was sitting.  Quick measurements in three places in the room and also in the reception area indicated slopes of 0.1% to less than 1.0%.  Staff in the office on this floor report that the floors slope in all the rooms.

I saw that the floors were not level on the 12th floor of the building.  Office staff were not conscious of this but they did say that previous tenants reported that the floors were not level.  I also saw the floor sloping down from a concrete column in an office on the 4th floor.

A staff member familiar with four floors in the lower part of the building reported that the floors were “Wavey.  Not very, very, very level.  We have to level when we do renovations”.

Building construction

The building is made of concrete – concrete foundations, columns and floors.

The foundations are supported on bedrock which is very strong.  I learned this from a friend who saw the foundations being constructed when his company worked on the building site.  He also said multistory buildings like this are erected quickly so they can be rented as soon as possible and make money.

Construction technique

The construction technique used to erect multistory concrete buildings is sensitive to construction schedule.

A concrete floor in a multistory building is constructed by placing concrete in forms that are supported on jack posts.  The jack posts are in turn supported on a previously constructed concrete floor below.  The floor below will also be supported on jack posts below it.  Jack posts are steel posts whose length can be adjusted – jacked up

You can see this construction technique in different places in Atlantic Canada – a number of jack posts at each floor level – usually three or four levels, below the floor under construction.  There are at least two buildings under construction now in Halifax using this technique, one on Jos. Howe Drive and the other on Young Street.

The technique involves removing the jack posts from the lowest floor and leap-frogging over the upper floors to support the forms for the next floor under construction above.

Construction schedule

I knew the construction manager who directed the work crews erecting the defective building years ago.  He told me one time – the chance remark, that he was on a very tight schedule to construct the building – had to get it up in a hurry.  Just like my friend said for multistory buildings, in general, but this one sounds like it was rushed even more.

Concrete strength

The jack posts are removed from the lowest level when the strength of the concrete forming the floor being supported just above is high enough.  The strength of concrete floors is specified by the design engineer according to the planned construction and use of the building.  Concrete sets up – gains in strength, over a number of days from the wet concrete when placed in forms to the rock-hard concrete later.  The quality of the concrete delivered to a building construction site is checked by testing companies to ensure it will set up to the design strength.

Analysis of the cause of the “wavey” floors

Building components

The defective, multistory building had five components when it was under construction:

  • Concrete columns
  • New concrete floor
  • Forms temporarily supporting the new floor
  • Jack posts supporting the forms
  • Recently constructed floors supporting the jack posts

Limited information

The limited information for a hypothesis in this case is:

  • Floor condition: – Sloping and sagging but usable
  • Building construction: – Simple concrete columns and floors
  • Construction technique: – Construct a new floor by placing concrete in forms supported on jack posts resting on recently constructed floors below.
  • Construction schedule: – The multistory building was put up in a hurry
  • Concrete strength: – Concrete gains its full strength over time
  • My experience during construction of one multistory building and examination of another during construction

Possible causes

Analysis of the limited information suggests the following possible causes associated with one or the other of the building components.  The causes are listed beginning at the top surface of the new floor:

Cause #1. The floor forms were constructed level but the concrete was not placed and troweled level by the concrete finishers

I believe the concrete was placed and troweled level – or to the level of the forms, an important qualifier.  I’ve seen concrete finishers at work often enough.  They are proud of their craft.  And besides, the concrete form they must place and trowel the concrete to is right there in front of their eyes a few feet away.  It would be difficult to make a mistake.

Cause #2. The floor forms were not level because mistakes were made in measuring the position of the new floor on the concrete columns.  These marks are the starting point for leveling the forms

Similarly, it would be difficult to make a mistake measuring the position of the new floor on the concrete columns.  This is a simple measurement with a tape.  I can imagine it being checked and rechecked.  “Measure twice, cut once” like a carpenter does.

Cause #3. The floor forms were not level, either because of the leveling method or because the posts were not jacked up properly

The jack posts would be placed according to the level of the forms and adjusted up or down a little as required by the form leveling technique.

Based on what I’ve seen on construction sites, I can easily imagine a carpenter’s level with a spirit bubble being used to check the level of the forms and the need to adjust the jack posts.  Cheap and quick on a job that’s in a hurry, also inaccurate.  Inaccurate in different directions too depending on where you put the carpenter’s level. This would result in different slopes to the floor forms – and different slopes and sags to the finished concrete floor like I saw in the defective building.

What I’ve seen – the plumb of concrete columns being set with a carpenter’s level – floor after floor after floor on one 20 story building.  Very crude.  It’s not too great a leap of faith to believe that the floor forms were set “level” in the same way in the 20 story building.

Cause #4. The forms sagged when the heavy concrete was poured because the distance between the jack posts was too great

This might be possible but unlikely because jack posts would be placed at the construction joints between concrete floor forms.  The forms themselves would be more than rigid enough to support a layer of concrete a few inches thick.  The forms are likely to be reusable – certainly from floor to floor, but also from job to job.

Cause #5. The floors sagged because the jack posts were removed before the concrete set up and was strong enough

This is possible.  I can’t dismiss it.  Particularly if low strength concrete was accepted at the construction site and there were only three floors of jack posts in place.  However, I might expect sloping and sagging to be more broadly distributed across the new floor rather than quite variable like in the defective building.

The floor in the long, narrow room on the 10th floor that tweaked my interest sagged 2 to 3 inches over about 10 feet.  And the slope was in a different direction in the square room about 25 feet away from the narrow room.

I also can’t imagine low quality concrete being accepted at a construction site – truck load after truck load and floor after floor.

But this cause is possible because I just don’t have enough information on how deflection three or four floors down would affect a new floor way up above.

Cause #6. The floors sagged because an inadequate number of the lower floors were supported with jack posts beneath the upper floor that was under construction

This cause might be possible if jack posts were placed at only two levels rather than the three or four that seem to be normal.  I see four in the two buildings I drove by recently.  It seems like a risky decision for a construction manager on a very tight schedule and in a real hurry to get the building up even if he’s prepared to accept low strength concrete.  I also don’t know as mentioned above on how deflection two or three floors down would affect a new floor.


What do I think is the likely cause of the “wavey”, sagging floors based on the limited evidence?

I think – my initial hypothesis, that the floors slope and sag – because the forms were not leveled properly – Cause #3 – in the rush to get the building up.


The following is what we do in forensic engineering when we think about the cause of a failure or personal injury for Counsel and the justice system:

  • Gather the evidence as limited as that might be and from whatever source,
  • Analyse it – carefully study each piece of evidence, note it’s nature and significance, how each piece relates, where each piece leads and what the whole tells us,
  • Identify and list possible causes, and related technical issues
  • Factor in our experience,
  • Think about and hypothesize cause – come down on one cause or the other,
  • Go gather more evidence
  • Analyse it – etc. etc.
  • Check if the initial hypothesis stands up to the new evidence,
  • Accept the hypothesis, modify it, or reject it completely and start over.

More evidence in the case of the defective, multistory building would be a precise elevation survey and contouring of many or all of the floors in the building.  Basically quantify the nature and extent of the problem, the defect whose cause you must determine.  But this is not likely to happen because the building although defective is functioning quite okay.  I’m sure there are others like it in Atlantic Canada.


  1. Bridge failure in litigation due to inadequate bracing – City of Edmonton.  But, inadequate for what?  Posted March 15, 2016