ABS = no skid marks. What do accident investigators check?

See the title. It’s self explanatory.

Where’s the evidence that a driver slammed on his/her brakes?

They hook up a data logger to the computer and down-load the last ten seconds that occured prior to the accident.


I’m not sure they can do that without a warrant, which they can’t get without “probable cause”, some evidence of a crime having been committed. That’s been being tested in the courts and I don’t believe the laws in most states have caught up with technology.

They’re investigating an accident. They can do whatever they want.


I do not think the average car stores that information. A few models are said to have a hidden “black box” but those are the exceptions. Typically, there may be no stored data whatsoever regarding brake application.

They’re investigating an accident. They can do whatever they want.

That’s like saying they’re investigating a Murder they can search your house or car without a warrant. Sorry…not so. If there’s probable cause then the police can easily get a warrant. But they can’t just search your car without one. There’s a case right now in Massachusetts where the police are pretty sure this guy has kiddy porn on his laptop…He’s suspected of indecent exposure to a child…But they are NOT allowed to search it and a judge isn’t signing off on a warrant.

Well the ABS kicks in when it detects a skid. Therefore there should be skid marks. They may not be a clear as with standard brakes, but they should be there.

I think this data is stored in the SRS (airbag) deployment module. Data such as speed.brakes on off maybe even G force data.Now if the bags didnt deploy I dont know if there is data. Some insurance companies are claming a right to this data when investigating a accident that a claim was filed for

Of course, I always thought that they couldn’t conduct wiretaps without a warrant either. Silly me, believing the Fourth Amendment actually meant something. (-;

Oh…they probably did…still doesn’t make it LEGAL.

I think though the skid might leave a very short line, maybe not visible, because of how abs works. Once it kicks in there probably won’t be marks. Smart guys out there, am I way off base?

Nope. ABS works in millisecond timeframes and completely stops the tire from slipping, even on snowy roads. There should be no skid.

I agree with Tester about a data logger but would something like this fall under a civil problem rather than a criminal one? If so, would this be a matter for lawyers in discovery to sort out rather than a warrant?

If drunken driving, hit and run, negligent homicide was involved maybe a warrant would come into play then?

Along these lines, I was involved in a wreck some years back in which a lady made a U-turn from the right shoulder across 2 lane of northbound traffic. I was on the inside lane and broadsided her after locking the brakes up and sliding into her.
They took me to the hospital and it was discovered later the investigating officer did not mark any skid marks on the incident report. This really put me on the hook when the lady denied turning in front of me. I had to go to court and won a judgment but the judgement was knocked down by 40% because of the officer failing to notate the skid marks. Failing to notate this added a tiny bit of doubt in the jurors minds.
(This officer was later promoted to detective, at least temporarily. He was busted back to patrol when he falsified evidence to cover up a screwup on a double-murder trial and which subsequently led to the acquittal of several suspects who were 99% more than likely behind it.)

JMHO, but I would advise carrying a cheap digital camera or picture phone in the car at all times. They passed a law in OK a few years ago requiring all cars involved in non-injury accidents to be moved off the roadway immediately. A few pics at the time of the accident could be invaluable because you just know if someone errs and causes an accident they are going to think about it and change their story 5 minutes later. It’s etched in stone. :slight_smile:

Driving is a privelege, not a right. We all may have allowed investigators to inspect the car however they want by signing to receive a driver’s license.

I read somewhere that they can follow the trail of brake dust.

Not according to more than a few court decisions, your auto (like your home) cannot be searched without your permission, probable cause, or a warrant. If an officer ever asks to search your car you have the right to refuse (and should do so), if they have a legal basis to search it they won’t be asking your permission.

There was an accident here in OK a few years back in which 4 teens in an Explorer overran a turning semi on a 45 MPH county road, swerved sharply, and plowed into a tree. Several were injured and one killed.

This investigation went on for several weeks and it was decided to turn this over to the DA for a further look since the one that was killed was a passenger and this could be a criminal matter. About 6 months later it was announced that the data was pulled as Tester mentioned and it showed that the Explorer was running 98 MPH when the brakes were locked and it left the roadway.

“Nope. ABS works in millisecond timeframes and completely stops the tire from slipping, even on snowy roads. There should be no skid.”

Yeah, but the tire has to be slipping to begin with, otherwise the ABS wouldn’t be activated. Seems to me that there’d still be some small skid evidence, it’s just far more difficult to see with the naked eye, since if the tire weren’t skidding the ABS would’ve deactivated.

Here in Ontario, if the “black box” or SRS module is seized at the scene of the accident, no warrant is required. However, after the car has been towed to the impound, a warrant is required.

Beyond that, there are other parts of the investigation like body damage, etc. that can help reconstuct what happened. And then there’s sometimes witness statements.

I think that the data logging feature was put in by auto makers mostly because they were tired of being sued by people who claimed that they were obeying a 30 mph speed limit when they lost control of the car and rolled over 8 times after skidding 200 feet.