The New York Times describes how video footage of police activity during protests at the Republican National Convention contradicted the official version of events, and led to the dismissal of charges against roughly 400 protestors:
A sprawling body of visual evidence, made possible by inexpensive, lightweight cameras in the hands of private citizens, volunteer observers and the police themselves, has shifted the debate over precisely what happened on the streets during the week of the convention....WorldChanging has more info on a similar case:
Alexander Dunlop, who said he was arrested while going to pick up sushi....discovered that there were two versions of the same police tape: the one that was to be used as evidence in his trial had been edited at two spots, removing images that showed Mr. Dunlop behaving peacefully. When a volunteer film archivist found a more complete version of the tape and gave it to Mr. Dunlop's lawyer, prosecutors immediately dropped the charges and said that a technician had cut the material by mistake.
In Dennis Kyne's case, an officer testified in vivid detail that he kicked, squirmed and screamed, forcing four officers to restrain him. But the case was dropped when prosecutors were presented with a video by a documentary filmmaker showing Kyne descending the library steps on his own power, with the testifying officer nowhere in sight.The folks at WorldChanging see recording devices in the hands of private citizens as comprising a "participatory panopticon." For those who don't know, the panopticon is a mode of surveillance based on an architectural form devised in 1787 by Jeremy Bentham. Most people think of the panopticon as a prison, but Bentham also saw panoptic systems as a "means of extracting labor" from workers, and as an ideal tool for regulating madhouses, hospitals, and schools. As regards prisons and the like, Bentham's goal was to increase hidden surveillance to a practical maximum, while relying on the subjects' assumption of continuous surveillance to have a normative effect:
[T]he persons to be inspected should always feel themselves as if under inspection, at least as standing a great chance of being so....It's very satisfying to imagine a reversal of this system, in which the many watch the few (needless to say, the innocent have nothing to fear). In reality, of course, the power relations are not quite that simple. The "participatory panopticon" is itself subject to surveillance, and to having its evidence seized and destroyed. But as recording devices get smaller, more inobtrusive, and more numerous, they may become effectively impossible to thwart.
You can find more information on how video documentation is being used to protect human rights here.