Just how good are the accident investigators?

[wendyg]

This absolutely just interested inquiry. I've seen the teams out examining the scene of a crash, and heard some of the conclusions that the investigators have drawn, but how exactly do they reach these conclusions, and how accurate are they?

There seem to be so many variables, including road surface, weather conditions, tyres, brakes, visibility etc etc, plus the obvious damage to any vehicle involved in an impact, and the damage to the people involved. Just how accurately can they piece together the events of a crash?

Any replies welcome, but esp from those who have relevant experience.

[mark69sheer]

They are pretty good but only when the evidence is there..

for example... they can tell from skidmarks how fast a car was going prior to an accident by how long they are and what the mass of the car is and the friction ratio of the road surface... They have a pendulum device that gets a reading from the road..
They can also do some pretty good guesswork about how the accident unfolded.. who hit what and when and where etc..

However...

They can only work with the evidence they have and if its raining and there are no skidmarks or the cars anti locks come on again leaving no skidmarks then they are limited in what they can deduce..
Also sadly they can also come to subjective decisions in certain circumstances depending on who is involved in the accident.
They have a difficult job working under very tight deadlines and generally do the best they can.
Infallible....no
a reasonable guide . . yes..

after all a driver can't claim he was only doing 30mph if his car demolishes two walls a bus stop and a bollard before stopping for example..

[Derek Smith]

The accident investiators use a book of calculations to come to many of their decisions about likely speed etc but these are under a bit of threat at the moment. It comes after major problems have been found with 'expert' witnesses. There were the cases of SIDS and following that, cases of arson as well. Many of the basics in fire investigation have been proved to be baseless especially in respect of evidence of arson. There is little doubt that there are innocent people wrongly convicted on the basis of duff expert witnesses. There is little doubt that the guilty will be let off as well because of faults with the expert evidence.

Mind you, such evidence should be scrutinised on a regular basis. If it is scientific based then science moves on at a startling pace. Everything I was taught by Mr Howles at school has proved to be wrong but he got his info out of a book written by people who were sure of their facts.

The use of expert witnesses is under scrutiny and will probably continue to be so for some time.

Generally, though, accident investigators are highly motivated, at least that's my experience of my force, and open minded.

[wendyg]

So if it goes to a court, do they go up as expert witnesses? How much is down to personal judgement?

[mark69sheer]

wendyg said:

So if it goes to a court, do they go up as expert witnesses? How much is down to personal judgement?

Their word adds weight to existing testimony.

If there are no other witnesses then their words have more weight but only as far as reasonable doubt unless the evidence is without question.

If there are witnesses coroborating their evidence then all the better if however witness evidence contradicts their assesment then their evidence will be viewed weaker.

I actually am glad they are around as in some cases they could be the only people on your side when needed if noone else was around to witness the event or the other parties suddenly find some witnesses.

[Derek Smith]

wendyg said:

So if it goes to a court, do they go up as expert witnesses? How much is down to personal judgement?

You cannot make guesses in court. Everything you say must be capable of being justified. You can say, 'in my experience' but these circumstances are limited and the evidence is virtually useless in cases where a quantity is being suggested. My experience is that all blue cars tend to do 30mph in such circumstances might well be the truth but it has little evidential value.

Investigators tend to err on the side of caution and give a minimum speed, which means that it is easier to justify if challenged.

A judge will warn a jury about expert evidence during the summing up. However, some experts, such as fingerprint specialists, will generate very muted warnings, while a psychiatrist's opinion will generate more of a 'Well, the bloke with the glasses reckons that this chap is as nutty as a fruitcake whereas his Jung following colleague says just the opposite so I'd ignore the pair.' Or words and phrases of similar meaning.

The evidence for the SIDS case was statistical but the basis was flawed. There was some suggestion that the conclusion were correct but, as they were not justified by the method used by the expert witness, they should not have been considered by the jury.

In my force we had a fingerprint expert match two prints and come to the conclusion they were identical. The SIO, a fastidious chap who was a real pain to work with, checked the evidence and found that the two prints were not only very identical, but the chap had matched the print from the form to, believe it or not, the print on the form. Must admit to having more time for the SIO after that. In the end the proper print was used but the mistake had to be released to the defence under disclosure and the expert was put through the mill at court. I've been a bit wary of experts since then. The actual print found at the scene was from a ribbed box so the SIO had been concerned that there wasn't enough evidence. So when the report came back with 84,000 similarities (perhaps not the correct figure; I wasn't involved in the job so there might have been some exageration) his suspicions were aroused. But it does make you wonder.

[cptsideways]

Having had a quite a bit of experience in the field of car control & sitting alonside people "losing it" on a regular basis which I do for a living much of the year. There is definately a fixed set of criteria you can work to when it comes to laying down rubber. Its predicatble, repeatable & can generally be analysed easy enough. The difference speed makes is expotential & is quite amazing to see the physical difference this actually makes especially to potential cornering speeds or trajectories in my case!

However the difference in tyres is truly astonishing & I cannot beleive they still don't take this into account (or appear not to) They appear to have one set of figures & thats what they work to against the surface friction taken.

I'd be very keen to learn a lot more about this, any of you PC boys fancy organising a day all about it??

[mark69sheer]

Expert witnesses don't allways tell the truth.

I went to court as a witness years ago when my father in law was involved in an accident..

he was pulling out of a driveway which was on a long curve..

A motorcycle with a pillion came speeding round the corner smashing into the side of his car and the pillion rider was badly injured..
The case was a prosecution against my father in law.
When the accident happened I went to pick my mother in law from the scene..
I pointed out to my father in law that there was an unbroken skidmark from the apex of the curve to the impact with his car... at the centre line.
I deduced he was travelling too fast and was unable to stop in time. the skidmark following the racing line proved also he was going too fast to be able to take avoiding steering action.
In court my father in law was questioned by the other parties solicitor.
The skidmark became a major point of discussion between all parties.
I was called to the witness box where I mentioned the skid mark...
In an effort to kill the skidmark evidence the prosecutions expert witness said that the rubber mark was not a skidmark but was in fact the rubber mark from the footpegs off the biks after the rider had deliberately lain the bike on its side in an attempt to avoid an inavoidable crash.
I have great pleasure in telling the expert he was totally wrong and that the model of bike involved had rubber on the treads of the footrests but actually had sacrificial metal balls on the end of the footrests so that they slid on the ground not the rubber and that the handlebars also nad domed metal ends so a bike sliding on its side would in fact leave silver metallic trails on the ground not black rubber ones which were therefore caused by the tyres..

cue red faces all round on the other bench and an early adjournment after quickly dismissing me..

Edited by mark69sheer on Thursday 28th February 00:35

[supermono]

wendyg said:

I've seen the teams out examining the scene of a crash, and heard some of the conclusions that the investigators have drawn, but how exactly do they reach these conclusions, and how accurate are they?

As a layman I can tell you that the investigations aren't worth the money. We see road closures for hours costing the UK squillions of pounds in lost productivity, and the recommendations? To put up speed cameras and set up companies in business to harvest the speed tax.

The result is world class failure in road casualty improvements.

So for the past 15 years (during which time the figures have stopped improving) we've been wasting money hand over fist and it would have been more beneficial to the UK for the powers that be to simply clear away the mess quickly and reopen the road.

After all the government and certain police cheifs already know that speed causes the accidents and speed cameras are the answers so why spend any money figuring it out?

SM

[vonhosen]

mark69sheer said:

Expert witnesses don't allways tell the truth.

I went to court as a witness years ago when my father in law was involved in an accident..

he was pulling out of a driveway which was on a long curve..

A motorcycle with a pillion came speeding round the corner smashing into the side of his car and the pillion rider was badly injured..
The case was a prosecution against my father in law.
When the accident happened I went to pick my mother in law from the scene..
I pointed out to my father in law that there was an unbroken skidmark from the apex of the curve to the impact with his car... at the centre line.
I deduced he was travelling too fast and was unable to stop in time. the skidmark following the racing line proved also he was going too fast to be able to take avoiding steering action.
In court my father in law was questioned by the other parties solicitor.
The skidmark became a major point of discussion between all parties.
I was called to the witness box where I mentioned the skid mark...
In an effort to kill the skidmark evidence the prosecutions expert witness said that the rubber mark was not a skidmark but was in fact the rubber mark from the footpegs off the biks after the rider had deliberately lain the bike on its side in an attempt to avoid an inavoidable crash.
I have great pleasure in telling the expert he was totally wrong and that the model of bike involved had rubber on the treads of the footrests but actually had sacrificial metal balls on the end of the footrests so that they slid on the ground not the rubber and that the handlebars also nad domed metal ends so a bike sliding on its side would in fact leave silver metallic trails on the ground not black rubber ones which were therefore caused by the tyres..

cue red faces all round on the other bench and an early adjournment after quickly dismissing me..

What motive did they have to lie ?
What was the outcome ?

(It doesn't ring true, speed to blame for a collision & the authorities saying no ????)

Edited by vonhosen on Thursday 28th February 07:11

[Dr Jekyll]

It wasn't the motorcyclist being prosecuted remember. Excess speed on the bikes part would weaken the case.

[telecat]

Watched the Program that was on a couple of months ago where an accident involing a Type-R was investigated. The investigation looked ok apart from one thing. The driver had stated that he thought he might have had a steering problem. When turning the wheel it "creaked". The investigator turned the wheel on the car and heard nothing. My thoughts were that the car had Power steering and the test meant nothing unless that power was being used. I think that they operate well providing that the base line is adhered to. Once other factors come into play they need to start looking at other options.

[Dwight VanDriver]

http://www.tinyurl.com/j8954

dvd

[telecat]

Dwight VanDriver said:

http://www.tinyurl.com/j8954

dvd

God Turn off the music please!!!!!!!!!!!!!!!!!!!!!!!!!

[mark69sheer]

vonhosen said:

mark69sheer said:

Expert witnesses don't allways tell the truth.

I went to court as a witness years ago when my father in law was involved in an accident..

he was pulling out of a driveway which was on a long curve..

A motorcycle with a pillion came speeding round the corner smashing into the side of his car and the pillion rider was badly injured..
The case was a prosecution against my father in law.
When the accident happened I went to pick my mother in law from the scene..
I pointed out to my father in law that there was an unbroken skidmark from the apex of the curve to the impact with his car... at the centre line.
I deduced he was travelling too fast and was unable to stop in time. the skidmark following the racing line proved also he was going too fast to be able to take avoiding steering action.
In court my father in law was questioned by the other parties solicitor.
The skidmark became a major point of discussion between all parties.
I was called to the witness box where I mentioned the skid mark...
In an effort to kill the skidmark evidence the prosecutions expert witness said that the rubber mark was not a skidmark but was in fact the rubber mark from the footpegs off the biks after the rider had deliberately lain the bike on its side in an attempt to avoid an inavoidable crash.
I have great pleasure in telling the expert he was totally wrong and that the model of bike involved had rubber on the treads of the footrests but actually had sacrificial metal balls on the end of the footrests so that they slid on the ground not the rubber and that the handlebars also nad domed metal ends so a bike sliding on its side would in fact leave silver metallic trails on the ground not black rubber ones which were therefore caused by the tyres..

cue red faces all round on the other bench and an early adjournment after quickly dismissing me..

What motive did they have to lie ?
What was the outcome ?

(It doesn't ring true, speed to blame for a collision & the authorities saying no ????)

Edited by vonhosen on Thursday 28th February 07:11

The case was a civil one brought by the insurance companies.
The traffic 'expert' on the other side had a vested interest to deceive the court.
He was an accident investigator which I believe can be a freelance role even within police investigations.

[Derek Smith]

supermono said:

We see road closures for hours costing the UK squillions of pounds in lost productivity,

I worked at Gatwick for a while and I was impressed by the BAA's method of rapid 'normalisation' after incidents. Their whole intent was to minimise disruption. The police, on the other hand . . .

There is little point in keeping roads closed for hours, and in some cases days, just to gather evidence that often is inconclusive and neither aids nor hinders a prosecution. I remember reading a massive report (skimming actually, and mainly the bits with pictures) on a motorway accident that had resulted in deaths. The conclusion was that drivers were driving too fast given the visibility reduction due to fog and the main bit of evidence to support this was a police driver who was overtaken by other drivers en route to the accident location. The phrase that stuck in my mind was something along the lines of: It was obvious from an early stage in the enquiry that the cause of the accident was drivers driving too fast for the foggy conditions.

There were a few CCTV cameras in the area but, according to the report, they were of little use as all they showed was the fog.

The report looked impressive. It had a picture of every vehicle involved, and, due to an upgrade in Word, had lots of graphs and pie charts, many in colour. But the chap who brought it to my attention said that, on reading it fully (the poor chap) there was this ponderous inevitability about the conclusion.

It was suggested that harsher penalties might deter drivers from speeding in poor visibility. So, not only will they be forced to crash into lorries and other vehicles, not only will they risk massive injury and death - possibly by burning, not only will many be so badly traumatised that they would require help for years, but we'll up the points on your licence from 3 to 4.

It was found, by the way, that there was no single driver to blame for the accident although there were prosecutions for minor offences but I can't remember the results.

The whole intent of the emergency services should be to secure the safety of the people - those involved, casualties and emergency staff - at the scene, to ensure quick and safe medical aid, either in situ or removed to hospital, identification of the casualties, i.e. which vehicle were they in, security of property, and then normalisation in a rapid and safe manner.

I can't swear to it but I think the motorway was closed for about a week. My friend's report on the accident, and others, was that the cost to prosecution ratio was the highest of any offences.

My friend was 2 ic of traffic, moved on from DCI on promotion (made him wonder why he bothered) and his boss had directed him to justify the department's request for more manpower. What he did was to go through all the major traffic incidents and come up with more efficient ways of dealing with them. He ‘saved’ more man-hours than his boss had requested and his extra staff did not require training.

He was moved on. I could never get him to say whether or not his report was a deliberate ploy to leave traffic.

He was a strong supporter of HATO, then just a suggestion, as if there is to be no prosecution then the police can leave the scene of an accident and HATO were quite capable of making the working area safe.

The enquiry into one accident in my force took a dedicated accident investigator months to complete (more than 4) resulting in no prosecutions although there were some sensible suggestions for road engineering which are just now, some 8 years later, being finished.

Unless there is obvious evidence of a serious offence (DD, death by dangerous) at an early stage of the enquiry, the police and other emergency services should concentrate on getting things back to normal.

[10 Pence Short]

mark69sheer said:

They are pretty good but only when the evidence is there..

for example... they can tell from skidmarks how fast a car was going prior to an accident by how long they are and what the mass of the car is and the friction ratio of the road surface... They have a pendulum device that gets a reading from the road..
They can also do some pretty good guesswork about how the accident unfolded.. who hit what and when and where etc..

If all the wheels continue to rotate under power during a skid then as far as I'm aware the speed of the vehicle cannot be accurately measured. It couldn't in my case.

Secondly Mark, you mention the civil court case, but you haven't mentioned whether or not there was a criminal case beforehand. Was there a criminal case, and if so, what was the outcome?

[mark69sheer]

10 Pence Short said:

mark69sheer said:

They are pretty good but only when the evidence is there..

for example... they can tell from skidmarks how fast a car was going prior to an accident by how long they are and what the mass of the car is and the friction ratio of the road surface... They have a pendulum device that gets a reading from the road..
They can also do some pretty good guesswork about how the accident unfolded.. who hit what and when and where etc..

If all the wheels continue to rotate under power during a skid then as far as I'm aware the speed of the vehicle cannot be accurately measured. It couldn't in my case.

Secondly Mark, you mention the civil court case, but you haven't mentioned whether or not there was a criminal case beforehand. Was there a criminal case, and if so, what was the outcome?

The police didn't take action.
The civil case was the pillion rider suing for damages.
Civil cases only require a balance of probabilities where as criminal courts require the removal of reasonable doubt.

The pillion passenger made a mistake..
he should have sued his mate who was driving instead.

[10 Pence Short]

What was the result of the civil case?

[WilliBetz]

One thing that amazed me with accident investigation is that it is possible to determine, from a broken light bulb, whether the bulb was illuminated at the time that it broke. Which is kind of handy if you want to know whether the motorbike was indicating left when the driver pulled out of a junction in front of it; or whether the driver of a car in a midnight collision had forgotten to turn their headlights on.

WilliBetz

PS. Derek - Thanks for your contributions to this forum. The more I read, the more I learn and appreciate your amusing, insightful and eloquent prose.