I don't know, but cops need more support with changes in policy (i.e. no arrest quotas), and more accountability would help.
Sgt. can't be with all his guys all the time. Some sort of measure of performance needs to exist, and arrest quotas are better than ticket quotas. People also don't realize that these things are often really low, The Calgary Police ticket quota is less than 30 per month.
In what way are police lacking accountability? Should Sergeants monitor live streams from each member of their team and question every decision they make in real time? Most agencies have in the last decade adopted the "risk management" approach to supervision, having Sergeants attend any major incident, and in those places guys have to check in with their Sergeant frequently even on minor calls.
Police already have additional paperwork to complete when they use any sort of force, and this is scrutinized. Arrests are taken to the prosecutor before charges are filed against an individual. Most agencies track their vehicles (and often their individual members) via GPS through the entire shift. Most places already use body cameras and dashboard cameras as well as in-car audio recording. Did you hear about the case a few years ago where two guys were blowing off steam and had a hypothetical argument about "How would YOU kill the chief?" and got fired when someone reviewed the tape?
I know it's a bitter pill to swallow, but the system works. All these morons that get killed by the police bring it on themselves by refusing to follow commands or drug intoxication leading to overdose or excited delirium.
There's not much more accountability that can be brought in other than a brain implant monitoring a guy's thoughts. His location is tracked from the moment he signs out his radio and patrol car, and any word his says in his patrol car is recorded. All of his encounters near his vehicle are recorded, and in most places every official interaction with someone is recorded, both by his own body camera and his partners. All radio communication is also recorded.
His supervisor reviews all of his reports before the package is sent to the prosecutor, meaning that two sets of eyes review all arrests (Traffic citations are typically only reviewed once unless challenged). An additional package is also created for risk management if there was any force used during the arrest, and these are often looked at by prosecutors too regardless of any accusation of wrong doing. After all, why wait?
Most places now only allow you to carry weapons issued by the agency and only use ammunition provided by the agency. All of these things have serial numbers on them. Agencies often stamp their ammunition so it can be traced, too. That's why they typically have their own armorer, or use one from a neighboring agency if they don't. This even includes intermediate weapons. Batons, OC spray, and Tazers all have their own serial numbers, and cartridges for tazers are individually tracked, spraying an area with a shit ton of little serial tags when the cartridge is fired. Notebooks are even often serialized. Policemen can buy their own pens, though (blue or black ink only.)
You tell me where there's room for more accountability in that.