As I’ve no doubt demonstrated by now, the Saturday Question is a bit of a misnomer. With that in mind, I happily unveil the Weekly Question. Maybe it’ll be on a Sunday, maybe a Tuesday. Stay on your toes!
At any rate, this week’s question was submitted by Annoying Mouse:
Recently, there was a fatal collision in my area. I am puzzled over how the police were able to determine who was where etc. I know from the witness statements they would have the general idea, but how do You/motor officers prove those statements? What is the orange paint around the front tires for, how do you measure or whatever with all the fire truck traffic and cops cars going across the tire tracks? A very sad accident when an innocent person is killed. Or maybe if this question is too detailed you could explain the training for accident scene reconstruction, what you have to measure and why.
There are a number of questions Annoying Mouse has asked. I’ll try to take them in order. First off, how we figure out who was where. We do take a number of witness statements. In my opinion, if you can get three to four independent witnesses that all more or less say the same thing, it can be fairly reliable. However, nothing is better than evidence. Evidence has no agenda, morality, point of view, or ability to lie. It simply is. Evidence will tell you exactly what happened…you just have to know what to look for and how to interpret it.
In some collisions, you can see a tire friction mark, or skid mark, leading to one tire or another. This may be able to give you a good idea where that particular vehicle came from. Not only that, but a measurement or two, plus some good old fashioned math, can determine how fast that car was going. (This is a simplified explanation, to be sure, but the theory is sound.)
The orange paint you may see around the tires notates the position of rest of the vehicle. At the scene, we will mark each tire and the center of same with the notation LR (left rear), RR (right rear), RF (right front), and LF (left front). The purpose of doing that is so when the tow trucks come and take the cars away, it’s still possible to have a good idea where the cars were. Ultimately, it’s best to shoot the scene (using Forensic Mapping equipment) while the cars are still there for more reliable accuracy. Sometimes, though, that is not possible. We do the best with what we have.
With regard to the Evidence Eradication Team (or Fire, if you prefer), we wait until they’ve come and gone to do the lion’s share of our evidence gathering. We shoot everything. Okay, not literally everything, but a lot of stuff. We shoot the basic structure of the intersection and/or roadway. We shoot the outlines of the vehicles at point of rest (if possible). If that is not possible, we’ll shoot them at the tow yard and put them on paper after the fact. This goes back to marking the tires. If we know where all four tires were at point of rest, we can put those vehicles back there later on paper. We shoot the tire friction marks. We shoot debris related to the crash. We shoot points of body evidence and/or bodies. (I went to a shoot once where we had over 80 different points of body evidence…it was a solo vehicle collision with one occupant. Looked like the car exploded).
Once we’ve shot the entire scene, we hook up the data collector from the Forensic Mapping equipment to a computer and download all the points. The program then literally draws the scene for us. Using that drawing, we can use some fairly involved math equations to determine speeds and, hopefully, fault.
Believe me when I tell you this is the Cliff’s Notes of the Reader’s Digest version of how the collision was investigated. I have completed over 400 (now 600+ as of 7/27/14) hours of Collision Investigation specific classes that I could not begin to do justice to in a post.
Hope that answered your questions, AM! Thanks for the question! I know you referenced some pictures and, originally, I posted them, but I was sent a message (appreciatively so) that posting pictures of a case that has not been adjudicated may present some issues…even though other news-related sites already have done so. I wouldn’t want my posting the pictures to create any issues for those involved in the investigation. And…just to assuage any curiosity…I was not nor am I involved in any aspect of the collision.
And that does it, folks, the inaugural Weekly Post. See? It’s Monday! Take that, Saturday!