Question about Police Lidar Standard Deviations

[Hacp]

You assume way too much. If the gun has a margin of error (which so far you've found no proof of) it's not always going to be over reporting speeds. It could just as likely under report speeds. And exactly how can you prove YOU were the one who got the very unlikely bad reading?

Stop doing wacky math and think for a second. The cop is going to say "I observed a car traveling at a high rate of speed in accordance with my training. I verified that speed with my Lidar unit +/- 2mph. Gave chase and ticketed the individual for speed violation."

Your response of "nuh-uh, bad gun" isn't going to work. Again, just promise you will come back and tell us how much the judge makes you pay.

An officer doesn't pull over someone going below the speed limit on this radar. Again, reference the link on psychology peer reviewed studies.

 

[lupi]

So, going with the I don't think I did it defense?

 

[Eli]

Hmm. What kind of car do you have? Is it possible you just spaced out for a moment while accelerating?

I'm actually leaning towards your defense here though. It does seem a little odd. I mean, there was a car in front of you? And they contend you were going faster than the person in front of you, since they pulled you over.. and not them?

But good luck proving it, short of a time stamped video of your dash. I think your proposal is fine, but be prepared in that it may not exactly happen like that.

 

[Fanatical Meat]

Hmm. What kind of car do you have? Is it possible you just spaced out for a moment while accelerating?

I'm actually leaning towards your defense here though. I mean, there was a car in front of you? And they contend you were going faster than the person in front of you I assume, since they pulled you over.. and not them?

I've heard this in traffic court its irrelevant because the cop could only pull over one.

 

[yh125d]

Pay the ticket, save the time you're wasting trying to get out of it (your time has value too) and if it's still bothering you buy a dashcam that tracks speed to make sure it doesn't happen again

 

[pete6032]

Wasn't there a story recently about cops not calibrating their LiDAR units? Or was it radar? I be too lazy to look them up.

I've used LIDAR for traffic studies before... hate those pieces of shit. So many times I couldn't register a reading while trying to blast the license plate. And one of them ran off a car battery I had to hump through rough terrain.

Just curious what kind of work do you do?

 

[Eli]

I've heard this in traffic court its irrelevant because the cop could only pull over one.

Funny! My last speeding ticket... like 10 years ago..

Rural, 55mph two lane highway... middle of no where. Doing ~65mph with a red 90s Toyota pickup cruising along behind me. Come up on a big rig. We slow and wait for an opportunity to pass, taking it up to ~75mph as we do so. But when I get over, the Toyota keeps on it, and passes me. I follow - doing about 85, but slowly slowing down.

As luck would have it, a state trooper pops up over one of the next little hills, cruising the other way, no time to react. He passes. No lights. Good. I look in my rear view, and he's doing a U turn. Uh oh.

He flies by me, and begins to pull over the Toyota.. For about 10 seconds, I think I'm safe as I slow to let them pull over. Maybe he only clocked the Toyota.. Then he rolls down his window, sticks his arm out and makes aggressive pointy motions towards the shoulder at me. Crap. 78 in a 55. lol

 

[Imp]

Just curious what kind of work do you do?

Used to be in traffic/transportation engineering (sub-branch of civil).

 

[DrPizza]

Doesn't say that's a standard deviation.

You seem to be assuming that it's a normal distribution. I'm not saying that you definitely were speeding, but given what you've said here, I really don't think you have a case to defend yourself. "I don't know how fast I was going, but I was behind someone and I know that no one would speed because there are so many cops on this road." "Sir, do you know WHY there are so many cops with radar/lidar on that road? "

Like someone above said, I've wondered what would happen if I was ticketed and I was pretty sure I wasn't speeding. I didn't have to wonder too long before I came to the conclusion, I'd end up having to pay the ticket, unless I got lucky by pleading not guilty. (Police don't seem to miss court around here.)

 

[Brainonska511]

This is the same effect plaguing psychology. Over half of psychology papers are not reproducible even though their results are accurate at 95% confidence intervals. http://www.nature.com/news/over-half...y-test-1.18248

It's interesting that you bring that up, because further research on that topic suggests that it may not be as bad as claimed. It's just that for some studies, in particular, those in psychology, context matters.
http://www.nytimes.com/2016/05/29/opinion/sunday/why-do-so-many-studies-fail-to-replicate.html
http://www.pnas.org/content/early/2016/05/18/1521897113.abstract

 

[freeskier93]

I was clocked going 73mph on a 55mph speed limit. I was not looking at the speedometer at the time so I don't know my actual speed. I was following the car ahead of me and cars usually go at the speed limit on this piece of the highway since police are always there!

Seriously man? You weren't paying attention, you were speeding, own up to it.

 

[MixMasterTang]

Please record your experience, it will be good for the lulz!

 

[Captante]

Doesn't say that's a standard deviation.

The issue we have here isn't if there is a "standard deviation" (I'm sure there is) ... the issue is if you can prove said deviation is the reason the cop registered you as exceeding the speed limit.

Last time a buddy of mine tried this, he was clocked with an old and quite inaccurate X-band radar gun. He tried the "when was it calibrated" argument, the judge promptly found him guilty. Why you ask? Because apparently all NY State troopers are considered "speed-experts" thus the radar fix was not required for a violation to be issued.

My guess is that you have never been to traffic court before correct?

 

[Brian Stirling]

You're not going to beat them with a suggestion of faulty LIDAR, I doubt Johnnie Cochran would be able to do so with a favorable jury. If you were far away it's possible he painted someone else but if reasonably close even that's off the table.

Best bet is to play nice and hope they take point off the table.


Brian

 

[Captante]

Best bet is to play nice and hope they take point off the table.

Exactly! :thumbsup:


Traffic court is about collecting money for the most part. There are two stages, first you meet with a prosecutor. If you are polite and humble at this point you will almost certainly be offered a greatly reduced fine hopefully with no license-points attached. Be smart and take it.

Second stage is a trial where you end up if you turn down the plea they offered in stage one. Be advised that you will almost certainly be found guilty here and if you annoy the Judge (my bet is you will) the fine will be SUBSTANTIALLY higher then if you had just mailed it in plus court-costs.

 

[pcgeek11]

Originally Posted by Hacp View Post
I was clocked going 73mph on a 55mph speed limit. I was not looking at the speedometer at the time so I don't know my actual speed.

I would love to see the judges face when you tell him this.

 

[Pulsar]

An officer doesn't pull over someone going below the speed limit on this radar. Again, reference the link on psychology peer reviewed studies.

So.... you think you're the smartest guy in the room. You're going to go in front of a traffic judge who regularly sees these cases and tell him, and the cop, that they don't know what they're doing and that statistically they're going to be wrong some of the time.... and that your case is one of those cases and you're sure of it.

I guess it takes all types.

 

[Hacp]

The issue we have here isn't if there is a "standard deviation" (I'm sure there is) ... the issue is if you can prove said deviation is the reason the cop registered you as exceeding the speed limit.

Last time a buddy of mine tried this, he was clocked with an old and quite inaccurate X-band radar gun. He tried the "when was it calibrated" argument, the judge promptly found him guilty. Why you ask? Because apparently all NY State troopers are considered "speed-experts" thus the radar fix was not required for a violation to be issued.

My guess is that you have never been to traffic court before correct?

Thanks. I am not using a calibrated argument. I am not going out there to proving that the device provided a poor reading. I just need to create doubt that it's always right then let the rest of my argument hold.

 

[Hacp]

You seem to be assuming that it's a normal distribution.

If you look at my original post I ask for more information on the distribution curves. Would you know anyone who has any?

"I don't know how fast I was going, but I was behind someone and I know that no one would speed because there are so many cops on this road." "Sir, do you know WHY there are so many cops with radar/lidar on that road? "

I'm confused because I am not going to say "I don't know how fast I was going". I am going to say I was going at the speed limit. My argument will be the last 3 paragraphs of that post. The first few paragraphs were just to answer the poster's questions. If you have any further information on the stats please let me know!

 

[Hacp]

So.... you think you're the smartest guy in the room. You're going to go in front of a traffic judge who regularly sees these cases and tell him, and the cop, that they don't know what they're doing and that statistically they're going to be wrong some of the time.... and that your case is one of those cases and you're sure of it.

I guess it takes all types.

I am going to provide a well researched argument based on evidence I have gathered. I would hope the judge would appreciate that I am taking this seriously.

Saw your name is pulsar. Would you have more info on LIDAR quality data? I saw that google was working on their own LIDAR device for self driving cars. Any google employees want to hook me up with non-confidential data?

 

[Hacp]

It's interesting that you bring that up, because further research on that topic suggests that it may not be as bad as claimed. It's just that for some studies, in particular, those in psychology, context matters.
http://www.nytimes.com/2016/05/29/opinion/sunday/why-do-so-many-studies-fail-to-replicate.html
http://www.pnas.org/content/early/2016/05/18/1521897113.abstract

Thanks for the link. It looks like the new study is weak since it is one that "suggests" a result. It does not perform the same study for other fields and compare results to psychology.

 

[Fritzo]

My wife was a cop. This is how it works:

The device is certified at certain intervals. If the device is in a certification timeframe, you're not going to be able to prove the device is defective.

What you CAN do is go to court and state that you feel road conditions/etc may have contributed to a bad reading. They may reduce or dismiss the ticket if it's your first offense. If the cop doesn't show up to court (which is a possibility), you get off scott-free.

Also, I wouldn't recommend going to court with a bunch of Internet articles and trying to look like you want to outsmart the legal system. Judges hate that and you'll be chastised. Traffic court isn't like Perry Mason.

 

[jlee]

Thanks for the reply. I am not trying to prove the cop is wrong. I am not trying to prove that the device is faulty. I will not be rude. Instead I intend to convince the magistrate or judge that there is reasonable doubt that I was speeding.

If that is all you accomplish, you'll still be found guilty.

http://criminal.findlaw.com/crimina...between-a-criminal-case-and-a-civil-case.html

Speeding is a civil offense, so the burden of proof is 'more likely than not.' Reasonable doubt comes into play for criminal cases, which this isn't (unless you're charged with a criminal offense, which I doubt).

LIDAR is laser, radar is..well, radar. Radar is (or was when I was using them in 2006-2011) calibrated and tested to +/- 1mph. This causes a possible margin of 2mph for moving radar (+/- 1mph for the base vehicle speed and +/- 1mph for the target vehicle speed).

That said, in five years of operating them, I have yet to see one that was obviously faulty. Speed always tracked dead on with GPS and (calibrated) speedometer. I didn't use really use a laser (not a huge fan of stationary with a handheld device) but I also haven't heard of it providing inaccurate readings. Of course, anything is possible...but given that you yourself have no idea how fast you were going, I don't see this ending well for you.

 

[jlee]

Thanks. If you have further details please provide it.

I was clocked going 73mph on a 55mph speed limit. I was not looking at the speedometer at the time so I don't know my actual speed. I was following the car ahead of me and cars usually go at the speed limit on this piece of the highway since police are always there!

I'm confused because I am not going to say "I don't know how fast I was going". I am going to say I was going at the speed limit. My argument will be the last 3 paragraphs of that post. The first few paragraphs were just to answer the poster's questions. If you have any further information on the stats please let me know!

And people think it's ridiculous that a police officer's witness of an event generally trumps the alleged violator's...

 

[Hacp]

My wife was a cop. This is how it works:

The device is certified at certain intervals. If the device is in a certification timeframe, you're not going to be able to prove the device is defective.

As I said, it is not my intent to prove the device is defective or that the operator (cop) didn't use it properly. It is my intention to show that even with everything working properly, it is likely that if an officer runs 40 readings a day he will catch 5 people in a month going 15 mph or whatever number faster than they were actually going. Numbers can change given actual data!