It seems like there is a smoking gun in this case (though I didn't review the evidence thoroughly). Widespread availability of video recording and distribution has provided many more smoking guns. Certainly, there are many more incidents where no smoking gun evidence is available. For a long time, black Americans have been claiming that such things happen and were widely ignored or disbelieved. It was and is a grave…
2) Develop systems that are structurally uncorruptable and uninfluencable as best as they can be, by having significant separations of power by design. There must be no incentive for those with the power to audit to be influenced by those they're auditing.
3) Probably many, scarily enough. Corruption runs deep in many societies that tend not to be considered corrupt.
In this case, I like the idea that the officers should be sentenced to prison at some level proportionate to the amount of corruption they were responsible for. The wrongly imprisoned should be released, and the State responsible for implementing the auditing controls against these officers should be forced to provide the wrongly imprisoned the average (for a given value of average) wage, or a multiple thereof to account for additional damages, for the entirety of the time they were wrongfully convicted and imprisoned for. That way, there's a personal incentive not to be corrupt in that if you get caught you are heavily personally punished for said corruption, and there's a strucutral incentive to implement effective anti-corruption controls as the state is then responsible for those that represent it.