1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Real life tire mark analysis; help me prove I'm innocent

  1. Oct 6, 2012 #1
    I am hoping you all could help me. I have been accused of a felony based on these tire marks. I did not make these marks! I do not even think my truck is capable! I am wondering if there is a way for the law of physics to prove this. I am posting all of the information I have that I thought might be relevant. I will get (or at least try) any other info needed. Please help me!!

    It is a single cab 4x4 diesel pickup, weight is 5820 lbs. Distance from center of L front tire to center of R is 67 inches. Wheelbase is 137 inches.

    The marks as recorded by the CHP:
    All measurements were taken at right angles to the station line.

    Item 1: Centrifugal/acceleration skid mark from V-1, increasing in width from its starting point.
    Begins: 28 feet of station point 0+37
    Continues: 15.5 feet left of station point 0+45
    Continues: 7.5 feet left of station point 0+64
    Continues: 13 feet left of station point 0+78
    Continues: 25 feet left of station point 0+82
    Ends: 34 feet left of 0+78

    Item 2: Centrifugal skid mark from v-1
    Begins: 10 feet left of station point 0+53
    Continues: 9 feet left of station point 0+64
    Continues: 15 feet left of station point 0+75
    Ends 28.5 feet left of 0+77.5

    Any help is greatly appreciated!!
    Is this even possible or have I been watching too much CSI??
  2. jcsd
  3. Oct 6, 2012 #2


    User Avatar
    2017 Award

    Staff: Mentor

    Ask an expert, not random strangers in a forum.
  4. Oct 6, 2012 #3


    User Avatar
    Staff Emeritus
    Science Advisor

    I don't think there's enough information here to say anything. That and I have no idea what all your numbers and stuff mean. (Station line? 0+X? Etc.)

    I think you need to get a lawyer and talk with them about this if you haven't already.
  5. Oct 6, 2012 #4
    Thank you for replying Drakkith. I was going with a public defender since I am not in the financial situation to pay a private attorney but he is worthless.

    I took some physics but I don't remember a whole lot. Here is my thought process:

    Those numbers are in feet based off the predetermined "station point" which is basically some random point they chose to base their measurements on.

    So if the station point is 0-0 then
    x= -22 y=37
    x= -15.5 y=45 etc...

    If you load them into the graphing calculator you can see what the marks looks like. I was hoping to be able to say that it is impossible for my truck to be able to make those marks based on size alone. They are circular "doughnut" marks. My truck does not make turns like a small car (ie: I have to swing wide to make it into my driveway).

    I thought there would be a way to exclude my truck simply because it is too big to have made these marks.

    I apologize if I am out of line here. I would just like to know if it can be figured and how.

    Thanks again for any help.
  6. Oct 6, 2012 #5


    User Avatar
    Staff Emeritus
    Science Advisor

    I dunno man. Those are pretty big donut marks. I mean, it's 40-50 ft between some of your points.
  7. Oct 6, 2012 #6


    User Avatar
    Science Advisor
    Gold Member
    2017 Award

  8. Oct 6, 2012 #7
    Thanks for taking the time Drakkith. That is what I was coming up with too so I thought I was doing something wrong. According to what I graphed out it would take a bus to have made those marks.

    The police report is so messed up. They didn't take any pictures of these marks and I never seen them. I went out there to look after I seen the report and they weren't there. Nothing makes sense. I guess I am going to have to start asking family for money to hire an atty. I really thought they would figure out that I didn't do this.

    Thanks Borg I had already seen those. Most of the skid analysis stuff is about speed and I couldn't find anything similar to my scenario.
  9. Oct 7, 2012 #8
    Start documenting all this information yourself. Who witnessed the vehicle making the marks? Honesty if there are no marks, then no crime was committed.

    Also were there two marks or one mark from the acceleration. Two marks indicate a mechanically locked differential. Your truck probably has an open differential which will only make one mark on acceleration.
  10. Oct 7, 2012 #9


    User Avatar
    2017 Award

    Staff: Mentor

    Well, the whole case (as presented here) looks strange. Based on those marks, you can conclude that a car was there - it might be possible to estimate wheel distances, acceleration and whatever, but even if that is sufficient to determine a specific car type (which I really doubt): There are many cars of that type*.

    *unless you have something really special, but then money for a lawyer should be no issue.

    So I think there is more into it, but that is not related to the tire marks.
  11. Oct 7, 2012 #10
    We need to know the truck and modifications done to it.
  12. Oct 7, 2012 #11


    User Avatar
    Science Advisor

    I rather think that there is nothing in the tracks to rule your vehicle out, certainly not without an expert opinion.

    You might want to have a look for pro bono lawyers if money is a problem - a quick google turned up http://www.probono.net/, which might be worth a look. Even if you can't afford a lawyer full time, you could consider consulting one for advice on and off but do the legwork yourself. If so, make sure that you think carefully about questions you want to ask before you go in.
  13. Oct 7, 2012 #12
    Thank you all for the responses! In all honesty I do not even know if those marks ever existed. I didn't know anything about them until 2 months after the fact when I saw the police report. I went out there as soon as I heard these allegations and there were no marks. Amazingly, the officer took no photos. The report claims that the officer noted "knobby" mud/snow tires that were consistent with marks at the scene. I didn't have mud tires I had highway tires and receipts and photos to prove that. The police report is dated for the day before the incident even happened. One of the officers that took my statement that night has since been arrested on assault weapons, controlled substance, child pornography and some other charge to do with him keeping people's id's and CHP records at his house. You would think that there is enough here to give me the benefit of the doubt but the DA is insisting on sending me to jail. After a lot of phone calls to family yesterday I have come up with enough (at least I hope its enough) to hire an accident reconstruction expert. I can only do one or the other (attorney or expert) and if the expert can prove there is no physical way things could have happened the way the other party says then I won't really need an attorney. There has to be some way to prove that I didn't do this. Sorry I went off on a rant there...

    I was assuming that it might be relatively easy to exclude my truck if indeed a small car made those marks. Obviously that is not the case. If anyone is up for the challenge and can think of anything that might help me prove my case please feel free!!

    HowlerMonkey is is a stock 1992 DODGE W250 CUMMINS TURBO DIESEL 5.9L 4x4
  14. Oct 7, 2012 #13
    The report just says, "Centrifugal/acceleration skid mark from V-1, increasing in width from it's starting point."
  15. Oct 8, 2012 #14


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    I've had a go at plotting it using Excel. Don't rely too much on the smooth version as not enough data points.

    Attached Files:

  16. Oct 8, 2012 #15
    Good news!! The public defender was able to get his boss to ok the cost of the reconstruction expert. So it looks like I am going to get the expert opinion I needed to clear my name and I don't have to ask my family to carry the financial burden. That is a big weight off my shoulders.

    Thanks again to all who offered to help!!
  17. Oct 9, 2012 #16


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    I think I would write to the prosecution asking to explain the above.
  18. Oct 9, 2012 #17
    One thing, I am not sure has been mentioned. In my country as in Yours, if someone accuses You of a crime, they better be able to prove it. If they screw that up, You do not have to prove a thing. Not Your problem if they cannot even gather evidence and present it. The onus is on them. I know this much and I am not even a lawyer, so sure your one does. Even so, always good to slam dunk your case with proof of your own. Never hurts.
  19. Dec 14, 2012 #18
    I thought I would update you guys if anyone is still interested. It wasn't looking too good for me so I ended up hiring a accident reconstruction expert and I finally got the report. My case is still pending so my fate is still unknown but I hope that this enough to prove that I am not the one that is lying. What ever happened to innocent until proved guilty?

    The expert went out to the scene and the marks were still there along with the paint marks from the CHP “investigation.” I then met him in a parking lot and we did a bunch of bunch of “tests” and he took hundreds of measurements with his fancy laser. He was able to prove that my vehicle was not capable of making that tight of a turn. The report is long but he made several points that excluded my vehicle from doing what the so called witnesses claimed.

    I just wanted to say thanks again to those that tried to help. It’s unfortunate that it is costing me a small fortune to prove my innocence but a charge like this would ruin my future (public service) career.

    I hope this nightmare is almost over...
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook