What do people think these cameras will achieve?....i suspect nothing.

how long can they video? How long can they actually remain active?

If the camera shows a policeman doing his job properly...OK

but what if there is malpractice, dispute about conduct or evidence that puts a prosecution in a bad light?

Technical problems will prevail?

Maybe the officer forgot to turn on the video?

Maybe the video is "lost"? "Damaged", "edited" "unclear" "time is changed or disputed.......

to me leaving these videos in the hands of a police force whose training to say the least leaves a lot to be desired and whose adherence to modern scientific procedures seems as best tenuous, is nothing less than asking for trouble.

""What Orwell failed to predict was that we'd buy the cameras ourselves, and that our biggest fear would be that nobody was watching." -Keith Jensen

In some places in the U.S. it's actually unlawful for the public/bystanders to video-record the police in action. Thailand seems to pick up on such abuses quickly - I have no doubt there'll soon be a similar prohibition in Thailand.