I can see an overwhelming case against armed police being made to use handheld video cameras whilst carrying out armed responses, and a rational argument against a bulky harness-mounted chest camera, but none against a helmet-mounted one (or, indeed, an independent recording officer being present at a pre-planned encounter like the recent police shooting that inspired this post: https://www.theguardian.com/uk-news/2017/jan/05/man-killed-by-police-m62-shot-chest-postmortem). The technology exists and is cheap and reliable.
The arguments seem unassailable to me. If the police acted correctly under the circumstances, cameras will help them to demonstrate this in court and to the public. This will help to deter unfounded legal action against them, saving law-enforcement budgets for enforcing the law. It will also help to maintain faith in the integrity of the force, bringing concomitant benefits including the reduction of violent attacks against police and police property, again protecting budgets and, more importantly, lives.
If they acted incorrectly (a cold term, I know, if someone has been hurt or killed), then video evidence can and should be used to protect the innocent. Not everybody who is shot by the police is a criminal or carrying a weapon (which, though illegal, dangerous and effing stupid is not, per se a capital offence) – ask the family of Charles de Menezes. More to the point, awareness that their actions are being recorded will deter any tendency towards the trigger-happiness we have seen in the US forces in recent years.
Armed police have to make split-second decisions in confused and highly-charged circumstances. They have a duty to protect the public from danger and every right to protect the safety of their colleagues and themselves whilst carry out dangerous duties. Quite rightly, the legal system and the overwhelming majority of the public recognise this and will always come down on the side of the police when there is a measure of doubt.
But the police have duties and responsibilities on their part, and amongst them is a responsibility to reduce the chance of doubt. When a cheap and reliable off-the-peg means exists to reduce the fog of uncertainty there is no good argument against implementing it. Indeed, failing to do so raises uncomfortable questions about the reasons why.