To the untrained eye it?s a pile of mangled wreckage, fit only for extending the Airport dump ? but to the professionals in the Traffic Collision Investigation Unit a crash scene can often yield the key to not only what happened but who was to blame.

No wonder they guard an accident spot as jealously as a detective would protect a murder scene.

Every piece of debris can be vital while every careless trespasser can blow a case.

Sgt. Val Holder, of the Traffic Collision Investigation Unit, gives an example: ?A headlamp bulb might be on the ground but still intact ? indicating the lights could have been working at the time. ?If someone kicks it and breaks it we don?t have that evidence.?

Worse still are people who ?helpfully? move bikes to free up a traffic lane, not realising that where a vehicle ends up in an accident has a lot to do with where it began.

But Unit head Sgt. Phil Lewis said a lot of accident forensics was based on the simple laws of physics, including Newton?s law of motion which holds that anything moving in a straight line will tend to stay straight until hit by another force.

Which can explain why a car travelling along a main road has suddenly veered in an unlikely direction after the unexpected intervention of another vehicle emerging from a side road.

Sgt. Lewis is not surprised by the number of accidents given the speeds people are travelling on Bermuda?s densely-packed narrow roads.

His job also has a lot to do with maths. A vehicle travelling at 30 mph covers 44 feet per second. ?The normal reaction time to a perceived hazard is 1.5 seconds so if you are travelling at 30 mph and there is a hazard 100 feet before you, you will have covered 66 feet before you touch your brakes. You have now just 34 feet in which to swerve or do something.

?That?s the same for all jurisdiction but in Bermuda there is very little margin for error with the narrow roads.?

Add fatigue or alcohol and reaction time will be much slower. ?Alcohol can delay you by up to four seconds. You can see why most fatalities happen at night.?

Even sober and awake drivers need to be aware as the brain takes longer to compute images in the dark said Sgt. Lewis. ?In a perfectly healthy individual reaction time can be as much as 2.5 seconds at night.?

But when those tragic miscalculations are made his unit is always on call to assist and piece together what happened. A lot can be garnered from spilled engine fluids ? which can indicate where the original impact occurred even if the vehicle has been moved.

?A collision scene is like a jigsaw which has to be put back together again. We start from where the vehicles end up and work backwards.?

Tyre tracks are another obvious sign and can indicate the speed a vehicle was going in said Sgt. Lewis.

Painstaking measurements of distances are taken ? a complicated accident can take up to five hours work at the scene and even more work back at the office. His team is armed with the latest equipment including a $6,000 machine which will work out the level of friction on a road, horsepower and acceleration rates as well as measure reaction time.

A software programme will electronically map out the accident scene. Ordinary forensics will help blow holes in people trying to pull a fast one after an accident said Sgt. Lewis.

Blood samples from a visor can reveal exactly who was in the driver?s seat ? if the injury reports haven?t already nailed the culprit. Sgt. Lewis said: ?In almost all cases where there is a front end impact the pedals will be forced back and the driver will have some type of ankle injury ? only the driver will have that.?

Broken wrists are another tell tell sign for who was holding the steering wheel.

?The Tariq White accident was a classic case where we were able to put a person where they were in the vehicle because of the injuries and the damage on the vehicle.?

And while drivers can be nursing broken wrists and ankles they normally fare better than others at a crash.

?The passenger is always the first person to get killed. The driver?s instinct is always to take some last second corrective action to save themselves ? unless it is a parent travelling with a child.?

Some drivers move to a passenger seat before the Police arrive ? the fact that the impact was on the passenger side but they don?t have the corresponding injuries while somebody else does, is a dead giveaway.

His unit has been stung by recent criticism following the Tyaisha Cox case where Sgt Lewis testified that the accused Melanie Wedgwood had done what any driver would have done. Ms Wedgwood was acquitted of the dangerous driving charge following the death of the six-year-old whom she knocked down on a Warwick pedestrian crossing in August, 2003.

But Sgt. Lewis said his job was to give impartial expert advice. ?I know a lot of people question the training we go through,? said Sgt. Cox in an office adorned with his 12 certificates from the Institute of Police Technology and Management at the University of North Florida, ?but we are entitled to give opinions because of our expert status.?

He is trained in every level of accident investigation up to research level having completed the first round of formal training way back in 1989.

The four-man team has seen a rise in cases on Bermuda?s packed roads even though fatal accidents averages were fairly constant.

?In relation to the early 1990s the average speed is easily 15-20 kph faster. The type of vehicles we are importing now have cruising speeds of 60-70 kph.

?Speeds at night are horrendous. People feel there might not be Police about.?