I'm not defending our system, but I do want to point out one problem with any ideal of how the system ought work. In reality, most of everybody will claim that they're innocent, including those that are not. And so from the perspective of anybody working in law enforcement/corrections, somebody claiming they're innocent is not only a criminal but a liar on top. And the vast majority of the time, they'd be right.
And every system enabling you to challenge your detention is going to be built with the knowledge of the sort of system it's working within. I live abroad now and in the system here defendants who lie about their innocence will face greatly lengthened sentences, so most people not only don't bother lying, but actually have to reenact their crime for police. But of course the obvious problem there is that it greatly increases the risk for challenging any arrest when you actually are innocent, though for a case like this (where there was 0 argument whatsoever that he was guilty) - that would obviously be a better system.
The police here are similarly allowed to lie. They're allowed to lie so forcefully that they're able to extract false confessions. It's not a rare occurrence.
And every system enabling you to challenge your detention is going to be built with the knowledge of the sort of system it's working within. I live abroad now and in the system here defendants who lie about their innocence will face greatly lengthened sentences, so most people not only don't bother lying, but actually have to reenact their crime for police. But of course the obvious problem there is that it greatly increases the risk for challenging any arrest when you actually are innocent, though for a case like this (where there was 0 argument whatsoever that he was guilty) - that would obviously be a better system.