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  1. #1
    Join Date
    Apr 2011
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    409

    Default GPS as Speed Data in Court

    My question involves a traffic ticket from the state of: Narnia

    This does not involve myself. A friend of mine received a ticket recently (claims was not speeding). This person also has a GPS device at all times on when driving. There is a way to download this information sort of like an aircraft "black box". They plan to dispute the speed via the GPS readout corresponding to the time on the ticket. Now, it probably will not be accepted in court unless sent directly from the GPS company and they are looking into doing that. Also, speed can greatly change within seconds and they are aware of this. The GPS system shows your exact speed for a particular timeframe and they think it's worth a try. It's also supposed to be accurate, but I'm sure like anything else this can be disputed. The device claims accuracy to +/- .01mph. Significantly better than the Ultralyte's +/- 1mph. This information is readily available online.

    Knowing traffic courts, it will be difficult, especially considering it is in favor of the defendant. It brings into question judicial notice as well. I told them since LIDAR does not have judicial notice in this particular state (Only NJ does) it would be unconstitutional to allow the state's evidence (without judicial notice) and not your own evidence (also without judicial notice). In other words, if the LIDAR is allowed, the GPS data should also be allowed if sent directly from the manufacturer.

    My question, has anyone ever heard of this being done as a viable defense?

  2. #2
    Join Date
    Sep 2005
    Location
    California
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    20,594

    Default Re: Gps As Speed Data in Court

    First, the REAL state could be important to know.

    Second, the specific time frame for GPS may or may not be valid because the time used on the citation may be off by a few minutes. Your friend would have to hope that his speed was constant for quite some time prior to coming to a complete stop. It might also serve to hang him if the data shows that he did, in fact, exceed the limit.
    **********
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  3. #3
    Join Date
    Jan 2006
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    38,867

    Default Re: Gps As Speed Data in Court

    Now, it probably will not be accepted in court unless sent directly from the GPS company and they are looking into doing that.
    It won't be accepted then either. Unless this specific GPS unit has been granted judicial notice or you can prove the accuracy of the unit in the situation at hand, it is not considered to be dependable data.

    Since I have no idea of the laws in Narnia, I do not know if the cops estimation of speed is an acceptable proof. I know it is in California if the cop is properly trained. I believe it is so in many other states.

  4. #4
    Join Date
    Sep 2011
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    OH10
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    17,019

    Default Re: Gps As Speed Data in Court

    I believe the ordinances of Narnia, are contained in the Chronicles of Narnia and can only be interpreted by a lawyer crowned in Narnia.

  5. #5

    Default Re: Gps As Speed Data in Court

    Quote Quoting lostintime
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    The GPS system shows your exact speed for a particular timeframe

    Wrong, any speed over a time frame (i.e. non-instantaneous) is an average speed. Average speeds can work to convict a person (i.e. VASCAR or aircraft if they're allowed) because the only way to get an average speed over a speed limit is to have an instantaneous speed over the speed limit. However, just in terms of pure mathematics, the opposite doesn't hold true. As such, you're not only going to need to know the accuracy of the unit, but also how long the sampling period is. Unfortunately, if the speed calculation for GPS works the way I think it does (distance between current location and last sample divided by time period, converted to MPH), then there's major flaws regardless of the time period.

    If the time period is short, then it's hard to argue that the average speed is too far off from instantaneous speed due to speeding up or slowing down. However, the margin of error for determining your position plays a much bigger roll. If the time frame is longer, then there's a higher chance that changes in instantaneous speed will be able to effect the instantaneous speed (i.e. speed up over the limit, then slow down, and have it average out between samples).

  6. #6
    Join Date
    Apr 2011
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    409

    Default Re: Gps As Speed Data in Court

    I highly doubt it would be acceptable, yet it does pose an interesting question. I only wanted to examine its plausibility assuming the average speed was truly at the speed limit or under; and for a short distance if average speed was used, to the point it was clear they never went even 0.001MPH over via the GPS.

    In my opinion, if the average was well-under to the point it couldn't be disputed, the court would still find a way to deny it. Even if the readout had your speed down to the second for every second in a minute, it probably wouldn't matter. I was hoping someone possibly had heard of this defense being used successfully, in any state.

  7. #7
    Join Date
    Jan 2006
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    Default Re: Gps As Speed Data in Court

    Quote Quoting lostintime
    View Post
    I highly doubt it would be acceptable, yet it does pose an interesting question. I only wanted to examine its plausibility assuming:

    a. the person can prove using the GPS they were not speeding for a short period of time
    b. the average speed was at the speed limit or under

    In my opinion, even if the average was well-under, the court would still find a way to deny it. Even if the readout had your speed down to the second for every second in a minute, probably wouldn't matter.
    so, prove the accuracy of the unit you were using in the location you were ticketed at the time you were ticketed. If you can do that, a court has to accept the data.


    a. the person can prove using the GPS they were not speeding for a short period of time
    what about the rest of the time? I can prove their are times in every day I am not sleeping but since nobody sees me all the time, I can never prove I never sleep even if I claim it to be so. The same goes for your proof you were not speeding.

    b. the average speed was at the speed limit or under
    define: average. If you mean a sum of a group of numbers divided by the quantity of sets of numbers, check this out.


    59+59+59+59+59+59+59+59+59+59+59+59+59+59+61=887/15=59.133

    see? I was never going over 60 mph....WRONG. The only thing that matters is the instantaneous measurement.

  8. #8
    Join Date
    Apr 2011
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    409

    Default Re: Gps As Speed Data in Court

    It's not my ticket. I'm also not sure how GPS devices track speed or how long the intervals are. If it shows all acceleration/deceleration (meaning different speeds over a time interval - it could work) Only trying to gather information to help out a friend. I had wanted to know if anyone had heard of this being allowed, in any state.

    Essentially, it sounds like you'd need a constant-per-millisecond (with speeds printed out of every specific millisecond in that particular time interval) reading to even have a viable defense.

  9. #9
    Join Date
    Jan 2006
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    Default Re: Gps As Speed Data in Court

    . I'm also not sure how GPS devices track speed or how long the intervals are.
    ito start with, realize what GPS is. All it is is a means to determine a location. Then, if the device calculates speed, the accuracy would be determined by how accurate the unit is in determine location and comparing that to the time it takes to get from one check point to the next. I can imagine it would vary greatly between different levels of quality of the unit.

    If it shows all acceleration/deceleration
    it cannot show acceleration in a meaningful way. All it can do is provide an average speed for the period of time it uses.

    Essentially, it sounds like you'd need a constant-per-millisecond (with speeds printed out of every specific millisecond in that particular time interval) reading to even have a viable defense.
    maybe not that specific but you are on the right track. The only thing you would have to do if you had such a print out would be to prove the units accuracy which is beyond most typical people's ability.

  10. #10
    Join Date
    Mar 2009
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    LA LA Land
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    9,170

    Default Re: Gps As Speed Data in Court

    Here is a rhetorical question.... I'd like to know where is it that you get the idea that it is against your constitutional rights to take judicial notice of the state's evidence (California's, for example) regarding accuracy of Lidar, if/when/because it conforms to NHTSA testing and calibration standards and is in compliance with the periodic legal requirements while refusing to offer you the same simply because your evidence is simply ink on paper issued by the same manufacturer that made the GPS device?

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