07 September 2015

Pip Adam

Engineering Insight: Expert Witness

Any engineer can be called as an expert witness to discuss forensic evidence in a court or tribunal. What can they expect? Forensic engineer Stephen Jenkins shares some of his experiences in the Courtroom.

Being a forensic engineer can require some sleuthing, according to Stephen Jenkins, forensic engineer with over 36 years’ experience in incident and failure investigation. “You can still get grilled. A lawyer might start with ‘I see you have a degree in mechanical engineering, but we’re actually talking about the biological aspects of river pollution so your training is irrelevant. Why are you here as an expert witness?’ And you have to qualify your expertise in your response, ‘Well actually what we’re discussing here is fluid mechanics and free surfaces and I happen to be trained in that’.”

Mr Jenkins describes forensic engineering as “the analysis or presentation of technical evidence and material to lay courts and tribunals”. Forensic engineers are often called in when engineering issues are being debated or are integral to the case at a tribunal of lay members. Mr Jenkins has investigated fires, failures, car crashes, collapses and workplace accidents. He’s currently leading the technical team investigating how the Aratere ferry lost its propeller in the Cook Strait two years ago.

Time is of the essence

“A good forensic commission starts shortly after the incident,” Mr. Jenkins explains. Timing is crucial. “Even if you make it to the scene before they’ve started demolishing or cleaning up, you only have a day or two to collect the evidence you need. Sometimes you’re there weeks after a crash and you have to trawl down the gutters beside the road to find bits of glass and car to give you an indication of what might have happened.”

Although technology has gone from a “tape measure to 3D laser scans” during Mr Jenkins’ career, he says a forensic engineer still needs common sense, accurate observation and a strong understanding of the analytics he or she will use to complete an effective site investigation. This observation often involves microscopic analysis. “A little bit like Sherlock Holmes – you often wander round the site with a magnifying glass, although you take a lot of photographs and [like with Murphy’s law] you always seem to find the bit you want to see is missing.”

In one of his first cases, Mr Jenkins was at the site the day after the incident, but not in court until seven years later. “The whole case hinged around one photograph I’d taken,” he says. “It was absolute proof of a regulation breach and enabled the client to win a significant settlement.”

Eye witness evidence

As well as the hard evidence gained during a site investigation there are often eye witness statements. These can be problematic, as they are usually contradictory and often prove to be wrong. “You learn to anchor these statements to known facts like the reaction time of humans to unexpected events, the speed that a normal human can walk or run, the light levels that people can distinguish colours, the weight that can be supported by a particular beam. All these help to either reinforce or challenge the eyewitness recollections of events.”

The precise art of analysis

He describes the analysis phase as “design in reverse. It’s gathering together shreds of information and then turning them into a consistent story on which you can base your opinion of what happened and why”. Collecting and testing evidence has to be completed in a controlled way and needs to be available to both sides of a case. Investigators record the time and place of collection and a strong chain of custody is maintained if evidence passes from expert to expert.

There also needs to be agreement between the parties around test procedures and processes. This is particularly important if destructive tests such as chemical analysis or sectioning an exhibit to see what is inside are undertaken. Mr Jenkins says during this phase forensic engineers use well known analytical techniques such as failure mode evaluation, failure trees and logic chains. He says these techniques “can be used to demonstrate to people why you’ve reached the conclusion you’ve reached.”

Forensic engineers give evidence in cases ranging from insurance liability to manslaughter. Mr Jenkins has given evidence to Environment Court hearings, local planning hearings and in other courts.

When he’s working with a lawyer, he says he often starts by saying, “You explain the law so I can explain to you how that law is reflected technically.” As an expert witness, a forensic engineer can express an opinion deduced from evidence unlike a lay witness who can only present what they actually witnessed first-hand. This means they need to be able to explain engineering issues so a person who isn’t an engin-eer can clearly understand the evidence that supports the engineer’s opinion.

Defending your opinion

The bulk of the work an expert witness does happens outside the Courtroom. They can spend many hours, for instance, assembling evidence before the trial. A lot is at stake in a case where forensic evidence is required and Mr Jenkins points out that forensic engineers are often called on to defend the credibility of their opinion. For instance, “a lawyer might ask ‘Can you not agree that infrasound at five cycles per second could physically damage the internal organs?’ And you have to respond, ‘As far as I’m aware it never has and I’m not sure it ever will but, yes, I suppose it’s possible,’ because if you say, ‘absolutely not’ they are likely to present several hundred papers off the internet that say it does. You can’t defend yourself against an absolute, but you can say ‘I’m prepared to accept there is some doubt, but I’m pretty sure I’m right,’ and then it’s up to the judge or the jury or whoever you’re dealing with to put the appropriate weight on the evidence of either side.”

Giving evidence also demands a confident stance in the face of tough questioning. Mr Jenkins says “A lawyer might frame a question that can’t be answered ‘yes’ or ‘no’ but he or she’ll demand a yes or no answer. In that case generally, you look to the judge and say, ‘I can’t answer that question yes or no’. Then the lawyer might try again, and you’ll tell the judge again, ‘I can’t answer that question yes or no’. Eventually the judge will say to the lawyer, ‘Just move on’.”

In the face of all this, Mr Jenkins says one test of a good forensic engineer’s report is that nobody can tell which side prepared it. Impartiality is crucial as the witness’ first duty is to the Court – not to one “side” or the other.

The enduring appeal of forensic engineering

Mr Jenkins’ career as a forensic engineer started in Invercargill where an insurance assessor employed him as an engineer to help resolve industrial insurance claims. At the same time, he saw an article by Marvin Specter, the founder of the National Academy of Forensic Engineering in the USA; eventually he became the Academy’s first International Affiliate.

What still appeals to him about forensic engineering, all these years later, is easy to summarise: “It’s very analytical work, it’s interesting work, it’s intellectually very stimulating and intellectually very satisfying. It’s very different from your average engineering work.”