I have direct personal knowledge[1] of demanding 'dash cam' video only to have the police department tell the court it had become "lost and unretrievable". So the chain of custody is important.
[1] My sister-in-law is a public defender, and she demands it all the time and gets a variety of pathetic excuses why "this time" it is unavailable.
And let's not forget that traffic court isn't an episode of Law and Order. Walking in and dramatically demanding dash cam video over a couple-hundred dollar ticket is going to put a very annoyed look on the judge's face. For a simple traffic violation such as speeding, you'll never get to the point of "oh, but if you sync the timestamps between the two videos..." It's a rabbit hole that the judge just won't bother with.
If you're ever in this situation just hire a damn lawyer and listen to their advice.
As a hopefully humorous aside, this joke is as applicable to the way "nerds" view the legal system as it is to the way they view cryptography (though obviously in a more metaphorical sense): http://xkcd.com/538/
I had a feeling that was going on--to bad. For years, I
wanted cams on every Cruiser. They are cheap, but so
few police departments utilize the technology. I can
honestly say that I have been pulled over in Marin County
so many times, just because the vechicle I was driving
stood out(was old), or I was driving past 10 p.m. on a fri- sat. night. I can't imagine what immigrants have to go through.
I've even considered installing cams on my current vechicle.
reading (and watching on Youtube when available) about a bunch of recent beatings and shootings, i think it should be made into a law that a police officer may apply force only when the action is being recorded (by a helmet or Glass-style camera of the officer). Without recording on, police officers should be considered "off-duty" and be subject to regular rules just like any other citizen.
The reason evidence gathered in illegal searches is inadmissible in court is so there's no incentive for cops to perform illegal searches to 'get the bad guys'.
If the law said "the video has been lost" meant instant acquittal, the video technology would become radically more reliable.
[1] My sister-in-law is a public defender, and she demands it all the time and gets a variety of pathetic excuses why "this time" it is unavailable.