The problem is that the government is little better than thieves. I don't mean that in the abstract. Look at this video :
https://www.youtube.com/watch?v=d-7o9xYp7eE
The video has 2 sections. First, the professor explains the reasoning behind the 5th amendment ... and then a police officer points out how he does it.
Despite that I would agree that this officer is a pretty correct cop. Certainly you cannot call this guy bad or corrupt, and equally certain: he is a pretty smart guy.
He states pretty bluntly what the goal of a police officer is, in criminal cases. You probably think the goal is to arrest the perpetrator, but listen to the guy, it's not. The goal is a confession, the goal is maximizing convictions. Seriously, that's the metric they're judged on: number of convictions. Regardless of any other factor, and frankly using highly illegal tactics (though compared to European police I must say he is a saint). On top of that he has self-control that rivals the best monks.
The average cop, I am sorry to say, is not like this guy. The average cop is much more like Kelso from "that 70s show". The average cop became a cop because he could not get another job, but got accepted in the entrance exam, or (worse) because they enjoy having power over others. Or, like Kelso, a combination of both. They're morons, dumb to the point that people who know them wouldn't leave them alone with a lighter. They're interested in proving their power over others directly by humiliating them (generally in pretty benign ways, but ... like a high school bully that isn't an 8 year old anymore). They regularly screw up badly, and they desperately want to hide those screwups, at almost any cost.
This isn't controversial: everybody who knows a few cops knows this.
Can you imagine what interrogations tactics are when the cop is NOT a 20 year old military veteran with a strong sense of honor and very good observational skills, without good self control ? Oh wait, no need to imagine, just search it on youtube. Warning: actually doing that will not be pretty. Moron police officers shooting people for completely absurd misunderstandings, in scenarios that certainly look like a strong racism, sexism, and just general bullying component is at play.
Doing the same lookups for other forces, like for instance, searching youtube for videos of the UN's "blue helmets" in action ... is far worse. European police forces ... outright disgusting.
The problem is not law. You cannot reasonably argue that the problem is that we just need a few more laws and all will be fine.