Forensic photography – the expertise available in eastern Canada

I was enthused recently – last Sunday to be exact, to learn that we have some very good forensic photographers in eastern Canada.  People who are objective, thorough, and interested in what they`re doing – trying to get those perfect pictures that portray a traffic accident scene exactly as it is.

(Forensic terrestrial photographers to be exact.  In engineering we distinguish between aerial and terrestrial photography, between aerial and land or ground-level photography.  The distinction is important because I’m certain that low level aerial photography with drones will soon be in the traffic accident investigator’s tool kit).

This came out – my learning about the photographers and how they do their work, during a meeting Sunday in Amherst, NS, of CATAIR, the Canadian Association of Technical Accident Investigators and Reconstrutionists.  They have members in Canada, the USA, Singapore, Australia, and Brazil.  Visit

As their website states, CATAIR was “formed in 1984 initially to provide all accident investigators a professional and affordable mechanism in which to meet and share experiences and ideas”.  I experienced that sharing in the Amherst meeting as well as a good talk by one member on forensic photography, Ed Goodfellow with the Miramichi, NB police department.

I`ve been trying to attend a CATAIR meeting for about a year and a half because of my work in forensic engineering investigation.  I also rely on good and thorough photography.  And more recently because of my enthusiasm for the usefulness of low level aerial photographs taken from drones of engineering failure and accident sites. (Ref. 1 and 2)

CATAIR also use a test method in traffic accident investigation that is identical in principle to one that can be used in slip and fall accident investigation.  This is the “drag sled” method for testing the skid resistance of floors.  I`ve been investigating slip and fall accidents.

Why is a blog on CATAIR important to you?

I’m blogging on this topic because I think it’s important for you to know about CATAIR.  Their investigative and photographic standards appear to be very high, way up there.  Members get good training, and, sadly, lots of practice considering the frequency of traffic accidents.  Investigating and reconstructing accidents is a big part of their work and good photographs are essential.

I also want CATAIR members to know about getting aerial photographs of a traffic accident site from a camera mounted on a drone.  Members can get an idea of what is possible with this aerial photographic technique from the photographs inserted in the references accompanying this blog.  These cost my client a few hundred dollars for 2.5 to 3.0 hours on site.

Many of CATAIR’s members are existing and former police officers, but engineers in private practice, civil servants from different levels of government, and others also belong.  I was invited to join by both their Atlantic regional director, Ken Zwicker, an original  member, Nova Scotia, and their current president, Terry C. Lolacher, ACTAR #1297, Alberta.

Ed’s comments indicated that they try very hard to get the pictures that portray the accident scene exactly as it is.  To take pictures that capture the evidence.  The truth is all that matters; the facts.  Forensic photographers don’t process with Photoshop at all.  They keep their pictures in digital format, and don’t reduce the size.  If too large they send to Dropbox and let the client download from there.  I gather this is done in the interest of a client being able to zoom in on a small detail in a photograph and see it clearly.

Apparently, the Holy Grail in forensic photography at accident sites is getting a night picture that shows the scene as an observer would see it.  It’s not easy, and I’m not sure they’ve got it yet – the Holy Grail.

I think the Holy Grail’s days are numbered though based on what I experienced in Amherst last Sunday.  I also think that CATAIR’s members are going to take traffic accident site photography to another level – no pun intended, when they start taking aerial photographs from drones.  And readers are going to want this standard of site photography when its applicable to the investigation of engineering failures and personal injury accidents.


  1. A picture is worth a 1,000 words, possibly many 1,000s …
  2. New forensic aerial photographic method …




Experts don’t know everything – and when they don’t know, they research

“I expected you to know that and not charge for researching it.“

This was the gist of a recent exchange I learned about between a civil litigation lawyer and an engineer.  But, should he have known?

The lawyer was concerned about the engineer charging fees for researching a technical issue.  It so happened it was in an area of practice that was not so well defined in eastern Canada.  Hardly known at all for that matter.  In this case, information about the different ways of testing for a particular physical property of a material.  Also information on guidelines, standards and codes for evaluating the test results.

I also learned that the different test methods had their pros and cons.  One method had some acceptance in Ontario and the New England states but was not available in eastern Canada.  Identifying and carefully evaluating a suitable alternative method was necessary in this forensic case.  A poorly defined situation also existed for guidelines for evaluating the test results.

I thought about forensic investigations that I’ve carried out over the years.  Some with technical issues that I needed to research before the investigation could be completed.  Technical issues that come along once or twice in a forensic-engineering-practice lifetime.  It’s unreasonable to expect an engineer to be up to date on such obscure issues, unwise if he doesn’t research them, and wrong if he doesn’t get paid for doing the research.

Examples from my files of cases needing research

Very small tunnels don’t fail very often in eastern Canada – when was the last time you heard of one?  For example, pipe tunnels that carry utilities under infrastructure.  But when they do fail then soil liquefaction and tunnel driving methods might need to be researched – technical issues that don’t crop up very often at all.  An engineer would be wise to research the state-of-the-art for these topics.  I did in one insurance case but the party responsible for the tunnel failure unfortunately didn’t.

(Soil liquefaction is the process of a soil becoming liquid when vibrated)

Inadequate underpinning  Fluid-like concrete, ‘flowable fill’, is used often enough in eastern Canada.  But concern about the slight shrinkage of the concrete on setting up – small fractions of an inch, holds little interest.  It’s just a wee bit too exotic for day-to-day engineering where the interest most of the time is simply filling a hole in the ground.

Except when counsel wants to know if a building was adequately underpinned, and the magnitude of such shrinkage figures in the assessment.  Then this obscure, seemingly insignificant characteristic must be researched.

Investigating slip and fall accidents is another poorly defined area of practice in eastern Canada.  Even when a person is wearing standard footwear the practice down this end of the country is not well defined.  The guidelines and codes are virtually silent.

The obscurity goes to another level when a person in their bare feet slips and falls on a wet surface – that is supposed to be dry, in a public place.  What do you use to simulate a bare foot in testing skid resistance under these conditions?  (Research told me what)

Factor in complex slip and fall biomechanics and an engineer can’t get out of the investigative starting-gate until he’s done some research.  Some of this engineering is once-in-a-life-time-of-practice in eastern Canada, and I suspect in other areas as well.

How about a man who falls off a step ladder with a slightly bent leg, strikes his head and dies?  What kind of expected knowledge would guide an engineer on how to investigate whether or not the bent leg caused the accident?  There was none and there was nothing in the engineering text books either.  I found the answer when I researched the work done by movie stuntmen.

What about the man who struck an obstacle on the highway, lost control, drove off a cliff and died?  How to investigate if the obstacle contributed to the accident?  A literature search established that the answer was in speed bump research.  Checking that research led to a field investigative test method that established the contribution made by the obstacle.  Counsel for the RCMP got their answer from preliminary findings – it was too dangerous to continue with the field testing.

These problems

I’ve had all these problems and others cross my desk in recent years and my clients understood the need for research and my need to be compensated.

Figuring out on a need-to-know basis

As engineers and applied scientists, we often work on a need-to-know basis, figuring out what to do and how to do it when the need arises.  And often enough it involves research when the knowledge doesn’t exist in the locality where the failure or accident occurred and the engineer practices.

Engineers are educated and trained to investigate and figure things out based on first principles.  They don’t expect to know everything from the get-go.

I took about 57 different courses in getting my two degrees in civil engineering and they were all about first principles.  And studied a number of other subjects during a two year land surveying course.

Engineers must research poorly defined areas of practice

If there are myriad ways of testing the physical property of a building material then it’s smart to research the most suitable method for the locality where the failure or accident occurred.  Particularly when any one type of case doesn’t occur that often, and test methods might have changed in the interim.

As well, if widely accepted standards for evaluating the test results don’t exist in the area where the problem occurred then standards and historical usage in other areas must be researched.  This is the only means of gaining some understanding of the significance of the test results in the locality of interest.

Experts don’t know everything – and when they don’t know they do what’s necessary, they research

Counsel and the engineer in the situation quoted above would be better informed if they read some of the decisions by judges in the supreme courts in eastern Canada.  Go see what happens to experts who don’t research engineering practice that is poorly defined in their locality, and in many others.  See also what happens to counsel’s case and the client’s claim or defense.

It’s unreasonable to expect an engineer to be up-to-date on infrequently occurring problems in poorly defined fields of practice, unwise if he doesn’t research them, and wrong if he doesn’t get paid for the researching.