Law enforcement will seize and use computers and the data they hold as evidence to convict criminals, just like any other tool that they might be warranted to seize.

Courts will examine the evidence of what it did to determine what role it played in the offence and whether it supports the allegation.

Likewise police complaints authorities could do the same in principle against the police; if someone were to give them a warrant and the power to execute it.

If a thing happens in public that was unwarranted and can be traced back to a police force or how they deployed any equipment, they can be judicially reviewed* for any decision to deploy that bit of kit. It's more a matter of will they actually be JR'd and will that be review be just and timely. * - in my country.

I don't think it's much different from how they deploy other tech like clubs and pepper spray, tear gas, tazers or firearms. If they have no fear of acting outwith their authority , that's a problem.

In some ways it might be easier to have an 'our word' vs 'their word' defense when they shoot someone, compared to a computer program that might literally document the abuse of power in its code or log files.

"Oops i dropped my notebook", is maybe easier than, "oops i accidentally deleted my local file and then sent a request to IT - that was approved by my manager - asking them to delete instead of restore any onsite or offsite backups".