Meet the scientists!

A fatal crash scene is like a jigsaw puzzle. The only problem is that someone has left with the picture. It is down to collision investigators to find all the pieces and make the picture. I examine the scene, mark-up skid marks and scratches, examine the vehicles, look at the injuries on the body and record it all. I use cameras, survey equipment (theodolite), tape measures, microscopes and scenes of crime equipment, maths and physics. This helps me to reconstruct the moment of impact and, hopefully, why it all happened.

When I am called to a crash by other traffic officers I ask for the scene to be protected. When I arrive the road should already be closed and I can begin to examine the scene. I start at the end, where the vehicles, or casualties, have come to rest. By looking at damage patterns, injuries and debris, I am usually able to work out which way vehicles were travelling and how they collided. I have to think like the road users involved; could they have seen the cyclist/motorcyclist/pedestrian, were they using lights (by examining bulb filaments I can often tell whether lights were on). So, with brake bulbs I can usually tell whether vehicles were braking at the time. I will examine seatbelts to see whether they were being worn (marks on them often show use at the time of collision). I examine tyres to see if they were in good condition, whether the vehicles skidded, how thw vehicles moved. Pedestrian collisions usually leave ‘cleaning marks’ on vehicle panels, where dirt is wiped away, or skin and blood deposits. These can tell me which way the pedestrian was moving, how they were hit, and how they fell to the ground. Shoes often show ‘heel strike’ marks to help with directionality. I photograph and measure all the evidence. If possible, I will reposition (rmechanical reconstruction) the vehicles back together, on their marks. This often shows where the vehicles were – whether one was on the wrong side of the road. A photograph of a reconstruction will save a lot of written words. Finally, having collected bulbs, motorcycle helmets and ensured the vehicles are recovered, I will conduct some skid tests to measure the coefficient of friction and how well the tyres will grip that section of road. This is essential if I am to use maths to calculate the vehicle (or pedestrian) speeds. I will later mechanically examine the vehicles to ensure that nothing had gone wrong with them to cause the crash. I may go to the post-mortem examinations of the casualties. Often the injuries that they have sustained, together with the damage to the vehicles, indicate how the crash happened, how a pedestrian was standing at the time of the crash and who may have been in the wrong. This is extremely important to save innocent motorists going to court, or guilty motorists escaping from being prosecuted for offences, such as (Death by) Dangerous or Careless Driving, speeding, or other motoring offences. Sometimes, it may be that people die in crashes which become Murder investigations. For that I use the same skills – to reconstruct the crash and show how it happened. MOST IMPORTANTLY – I am a police officer, but I am much more a person of science. I am there to interpret the evidence for all of the court; the Defence, the Prosecution, the Judge and the Jury. I must act without fear or favour, or bias, to explain the evidence and the science to all.

I had two really inspirational science teachers – my biology teacher, Mr Porter, and a chemistry teacher, Mr Brown. It is really important that school students of all ages are inspired and enthused about science at a young age. We cannot avoid science – it is all around us, as I find in my work. The better the equipment in schools, the more likely that children will enjoy science and want to be a part of it. I left school with only ‘A’ levels. Last year I had the chance to go to university for the first time – that was because I still have that passion for science.