Justice isn't innocent people being convicted of crimes because evidence rules weren't followed. Our legal justice system is run by humans who are just as perfect as the ones committing the crimes, and the ones sitting in juries.

We give police, lawyers, and others in the criminal justice system great power over us - they're legally permitted to punish and physically restrain humans. That cases can be won on technicalities - when police, lawyers, etc break the rules that protect us from them - helps to keep them honest and trusted. That's how we watch the watchers.