No it isn't. People have imperfect memory, and if the police can knowingly lie to you, then they can also convince you to admit something which never happened, effectively coercing you to fabricate evidence against yourself.

Yes, it may lead to some bad guys getting caught who otherwise wouldn't have been. But that is not an excuse if it also compromises the rule of law for innocent people.

Yes, great, so if neither of you were actually involved in the crime and they tell you that the other guy gave you up, you can fabricate something that implicates him instead so they take the rap because you’re scared of being blamed.

This isn’t a hypothetical, people have literally gone to prison for decades before some new DNA evidence exonerates them and the ‘accomplice’ admits they lied…

To be clear the vast majority of folks who get cleared based on “new DNA evidence” or whatever actually don’t have their innocence proven. Instead in most of these cases, there is shown to be some problem with a piece of evidence relied on at trial.

To be clear, the prosecutors should be held to a high standard, and they should be forced to prove their case beyond a reasonable doubt. But we should also be a little more cautious about proclaiming the “innocence” of people whose guilty convictions are found to be problematic. In case that evidence had been excluded on time, it is possible that the prosecutors could still have built a solid case that relied on different evidence.

> about proclaiming the “innocence” of people whose guilty convictions are found to be problematic

That's literally how innocence works though. From the universal declaration of human rights: "Everyone charged with a penal offence has the right to be presumed innocent until proven guilty according to law in a public trial ...". If they weren't proven guilty they are presumed innocent.

Yes but it’s a presumption rather than something that is proven.

If the guy who done it was blonde, 6’2”, driving a red Mercedes, and he wrapped the body in a green rug, and it turns out that the bloodstains on green rug of the 6’2” blonde guy with the red Mercedes that you arrested for it are only actually 70% likely to be the victim’s rather than 99.5%, while LEGALLY the guy in prison now can benefit from the presumption of innocence, I’m not sure I’d be comfortable if he moved in downstairs.

Proven innocence would be “oh we have irrefutable video evidence that this guy was two states away at the time”.

This seems like a stretch. As far as I know, usually DNA evidence in exonerations is more along the lines of, "The DNA is 98% match for a known killer who was arrested for similar crime a few years later."

Even that is problematic. A 98% match means there’s a 1 in 50 chance that the sample is not from the person that it’s been matched to. How many cases do you have to cross match with how many felons before you get a false positive? It’s probably not as many as you think, but I don’t have the numbers to do the maths with.

Suggested reading on this topic: https://freakonomics.com/2008/08/are-the-fbis-probabilities-...

It has nothing to do with 'proving', since your ability to prove is always suspect. It's basic civics.

That’s sort of what I’m saying, these convictions getting overturned does not prove innocence, it just means that guilt is not proven adequately.

Interestingly enough this only works in countries where the police is allowed to imply they can get punishment lowered by talking to the prosecutor, something that's impossible in most western countries.

It unfortunately has a side effect, the reciprocating "my friend did it" defense works really well in those places - Scandinavia, I'm looking at you.

Given two murder suspects, but no witnesses, and no evidence of who actually delivered the final blow, it doesn't matter if both would be covered in the victims blood. As long as they point blame at each other and shut up, chances are they will get away with murder.

They would still very likely go to prison of course, but for some "lesser" crime like assault.

The police in other countries manage without doing this.