Our criminal justice system doesn't even begin to be that accurate. And particularly not where minorities are concerned. Just because the prosecutor thinks they can win has not much to do with whether the defendant is guilty.
If the prosecutor thinks they can win the person is very likely to be found guilty. That doesn't mean they committed the crime though. That's the problem.
Despite the common perception of "everyone in prison will tell you they are innocent", pretty much everyone I met freely admitted what they had done and was willing to discuss it at length. The number of people who are convicted through some sort of cheating is shacking. Not saying they are pure as snow never did anything, by any means.
You look through a guy's case and see that after months of surveillance and getting nothing the cops "got a confidential tip from a confidential informant", pulled a warrant and searched the house and found a kilo of cocaine in the refrigerator...of a guy who admits he was a trafficker who the cops never even thought before that night brought product into his house. It is hard to imagine that months of surveillance would not have netted something from a guy who is so stupid that he keeps a kilo in the fridge, so when he says it was planted you have to wonder.
Now, I tell that story to people and a surprising number say "Well, he
was a drug trafficker and he did belong in prison." That misses the point. The cops got this "windfall evidence" to convict him of distribution (which he actually didn't do) and could get just as solid a windfall should for some reason they want to convict
you...or you, or you, or you.
You look through another guy's case and he spent ten months in the county jail fighting his case and the case is dropped because the evidence looks like there is no way to get a conviction. He doesn't even make it out of the county jail before he is arrested again on the same charges. The evidence is the same. He immediately takes a plea deal. WTH?
When they refiled the charges
every adult member of his family was indicted as a conspirator. The case was still not winnable, but the nature of the charges screamed "flight risk" so just like the first time bail was extremely unlikely. So rather than have his kids and all his nieces and nephews committed to foster care he took a plea deal that included all the false conspiracy charges being dropped. It is listed as a stipulation in his plea, so it isn't something a bitter inmate just made up.
Again, the guy was growing pot. But the fact is they never did catch him at it or in any way prove it. But they did put him in prison for it. Using a process that would have landed him in prison whether he had done it or not.
Do these or similar stories account for every inmate? Of course not. I was caught, red handed as it were, and duly convicted. Plenty of people are. So many people are that it really makes you wonder why the cops feel compelled to cheat
at all. The obviously guilty seem like they really should be sufficient. But even though they don't account for every inmate, or even a large percentage of inmates, I can follow those two stories with a dozen more, easily, that would, or at least should, scare the heck out of every citizen who has, or even hasn't, committed a crime.