You can sometimes use a camera to take the measure of important technical issues during a forensic investigation.  And unexpectedly get the answers to your questions quickly and easily as I found out during one investigation.

I was retained by the RCMP a few years ago to determine if a pile of salt on a highway contributed to a fatal motor vehicle accident (MVA) – that was the technical issue.  I did this by carrying out field trials like they do in speed bump research.  These trials determine the effect of different sizes and shapes of speed bump on vehicles travelling at different speeds.

When I started these trials I didn’t know where they would take me except they approximated what took place during the fatal MVA – and involved measuring like engineers do.  There were no neat little formulae, no salt-pile-contribution-determining procedures in text books.  But I had to start somewhere – the way it so often is in forensic engineering investigation.  The end result was surprising in answering the question about the contribution of the salt pile.

I built a test site on a run way at the Shearwater airport like those for speed bump research.  I marked off a traffic lane on the runway the same size as that at the accident scene.by painting a centre line and shoulder lines.  I then constructed a pile of salt in the lane the same shape and size as that at the scene.  My tests would involve driving the vehicle in this lane, over the pile of salt and filming what happens – the effect.

Speed bump research records what happens to a vehicle at a speed bump by measuring and photographing its position in three dimensions:

• Side to side in the traffic lane between the centre and shoulder lines,
• Along the lane with a large ruler, and,
• Vertically above the lane with another large ruler.

I did the same at my test site.  The painted traffic lines oriented the vehicle side to side in the lane.  A large ruler consisting of 1.0 foot graduations painted on the asphalt down the lane from the salt pile located the vehicle in that direction.  Another ruler consisting of 0.5 graduations marked on a sheet of plywood set at the side of the lane opposite the salt pile located the vehicle vertically.

I retained three professional photographers to film the position of the vehicle as I drove over the pile of salt.

• One was in the cab with me to film what I saw and experienced.
• Another was in the bucket of a boom truck down lane and 50 feet above filming the position of the vehicle side to side in the lane.
• The third was off to the side of the pile of salt filming the position of the vehicle against the backdrop of the rulers painted on the plywood and on the lane.

I also staged the position of the vehicle on the salt pile and had this filmed from a sea king helicopter for illustrative purposes – you would use a drone fitted with a camera to get these pictures today.  The photographer with his camera is shown above in my blog site masthead.

The RCMP told me that the vehicle was travelling at a speed of 50 km/hr or more when it hit the pile of salt.  This was based on tests by their accident reconstruction specialist.  I planned to do my test at that speed but start at the lower speed of 20 km/hr and gradually increase.

I drove the vehicle over the pile of salt at 20 km/hr as the cameras rolled.  It was pretty well all I could do to keep the vehicle in the lane after striking the pile of salt – it did veer off to the right a little and this was captured by the camera man in the boom truck.  Striking is an apt term.  And it was all the camera man in the cab with me could do to keep his camera steady as the vehicle rocked and rolled.

We saw on viewing film of the vehicle against the backdrop of the big rulers that the vehicle got 2.0 feet of air on striking the pile of salt and the front wheels stayed aloft for 18 feet before landing on the test lane again.

The three cameras recorded about 30 minutes of film.  I viewed this film and edited it to a four minute film clip to include in a preliminary report to the RCMP.  I reported that I could not continue the testing at higher speeds until I had safety and rescue procedures in place for the driver.

The RCMP and counsel on viewing the film clip and learning of my need for safety measures stopped all further testing.  “No need to continue testing, we have our answer”.

They quickly saw in the film clip the effect, the contribution of the pile of salt to the erratic behaviour of the vehicle and its airborne trajectory at 20 km/hr.  It didn’t take much imagination to know how the pile of salt would contribute to a fatal MVA at a speed of 50 km/hr.  Seeing is believing when you’re taking the measure of some things.  That’s often more than good enough for the justice system.

But all of this was also quantified by filming and recording the 2.0 foot and 18 foot airborne measurements and the veering of the vehicle off to the side of the traffic lane.

The forensic investigation of many failures and accidents needs input from more than one engineering, scientific or technical specialist.  These cases require the services of a principal investigator – a “generalist” forensic engineer.

The role of the generalist engineer is recognized by the American Society of Civil Engineers (ASCE) in their Guidelines for Forensic Engineering Practice. (Ref. 1)

The engineer retained by counsel serves as a principle investigator as soon as he recognizes his particular expertise must be supplemented by that of others. He identifies these specialties, coordinates their efforts, studies the findings of each, synthesizes and analyses all data, including that of his own specialty, draws conclusions and formulates an opinion as to cause.

This process is almost always the case with catastrophic failures.  But occurs often enough during investigation of the small to medium sized failures that characterize forensic engineering in Atlantic Canada. (Refs 2, 3)  And I suspect in Canada in general.

These smaller failures are seldom alike.  As a result, few engineers get to investigate hundreds of a particular type of failure or accident and specialize in it.  I seldom see the exact same failure a second time and must consult with other specialties often enough to supplement my expertise.  Or research the subtle differences between seemingly similar failures and accidents.

For example, slip and fall accidents – five that I’m familiar with are all slightly different, one in an odd way, and foundation failures, land slides, floods, fires, soil-steel bridge collapses, marginal wharf failures, old fuel oil spills, buckled bridge beams, defective step ladders, vibrating buildings, etc.  There are lots of specialists in different fields of practice, but not in all, and those that are available are not necessarily just down the street and around the corner.

In spite of the variation, we engineers are still retained to investigate the problems that occur and we do this quite well.  We are recognized as problem solvers and qualified to “figure things out” – including when we must supplement our particular expertise with that of others.

We function as principal engineers – “generalist” engineers, and also as specialists in our particular field.  We have the following key attributes of experts, including today a couple of important additional attributes:

Key attributes of experts:

• Education
• Training
• Experience
• Skill, and,
• Knowledge

Important additional attributes of experts serving as principal engineers:

• Principal investigator, “generalist” forensic engineering skills
• Report writing skills (most disputes are resolved out of court today based on an expert’s report)

You might be interested in four examples of forensic investigations that needed input from several specialties, all directed by a principal investigator, a “generalist” engineer:

Example #1

I investigated the cause of a soil-steel bridge failure that permanently disabled a car driver.  During that investigation I retained the services of:

• A land surveyor,
• A hydrologist,
• Two engineers experienced with corrugated steel structures – one in Ontario, the other in Massachusetts,
• A metallurgist, and,
• A metal detectorist (person who locates buried metal with a hand-held electronic device)

These specialists took part in the investigation in addition to my own specialties in civil and geotechnical engineering.  They contributed to formulating an opinion on the cause of the bridge failure.

I functioned quite well as the principal investigator in this case – the generalist forensic engineer.  However, if this had been a steel or concrete bridge I would have quickly referred counsel to a structural engineer experienced in bridge design as better qualified to be the principal investigator.  I could have contributed by investigating the adequacy of the bridge foundations.

Example #2

In another case, the RCMP asked if I could determine if a pile of soil-like material on a highway contributed to a fatal motor vehicle accident (MVA).  The vehicle drove over the material then off a 75 foot cliff and into the sea.

I wasn’t sure until I realized the pile of material was an earth structure – a structure in the built environment formed of earth.  Civil engineers specializing in geotechnical work are well qualified to investigate earth structures.

But, I wasn’t out of the woods.  I researched the literature on the investigation of fatal MVAs involving obstacles on a highway, and didn’t find a thing.

But I did catch onto the fact that the pile of soil-like material on the highway was like a speed bump, and there was an extensive literature on speed bump research and design.  So, I investigated the effect of the material on the vehicle like it was a speed bump.  The investigation involved full scale field tests on an airport runway and a lot of photography.

The specialists assisting me as the principal investigator were:

• A helicopter pilot
• Three professional photographers
• A film editor
• Accident reconstructionist (the RCMP provided data gathered by their specialist on how the accident occurred)
• Boom truck operator
• Contractors to build the earth structure and paint traffic lanes on a runway

Example #3

The continuing and excessive foundation settlement of an industrial building 10 years after it was constructed – ongoing 10 mm settlement per year, is another good example of a principal engineer directing a forensic investigation.  Also, in this case, designing a method to stop the settlement.

It was an easy investigation of cause – I determined the foundation soil conditions and saw immediately that they were inadequate.  Fortunately, the soil conditions were also perfect for grouting as a way of strengthening the soils and stopping the settlement.

The investigation involved the following specialties including my own in civil and geotechnical engineering:

• Geotechnical engineer
• Structural engineer
• Land surveyor
• Grouting engineers
• Borehole drillers
• Peer review engineer

Example #4

A final example is the Edmonton bridge failure that occurred last March, 2015  This was a serious structural engineering failure.  I would not qualify to direct such an investigation but would qualify to contribute input on the adequacy of the foundation soils supporting the bridge.  Also, as a civil engineer, I can look at the elements in the failure and suggest possible causes, as I did last year.

I can easily imagine a principal investigator, a “generalist“ engineer, retaining the services of the following specialists during investigation of the failure:

• A micro-meteorologist (to assess the weather and winds at the bridge site at the time of the failure)
• A bridge design engineer
• A structural engineer
• A bridge construction engineer
• Off-site steel beam/girder fabricator
• Crane operator
• Foundation engineer
• Geotechnical engineer

References

1. American Society of Civil Engineers (ASCE), Guidelines for Forensic Engineering Practice, 2nd ed, 2012, page 9.  (ASCE has represented civil engineers in North America since the mid 1800s)
2. Forensic engineering practice in Eastern Canada.  Published May 7, 2015
3. What do forensic engineers investigate in Atlantic Canada?  Published October 9, 2014