2% of people on death row get exonerated and that’s an underestimate due to the difficulty in proving innocence. Most crimes don’t see anything close to that level of review before or after conviction with death row reserved for the most clear cut cases.
So, most estimates suggest in the range of 2-10% of convictions are probably wrongful.
Remember: the person started out in a position of presumed innocence, and were found guilty beyond a reasonable doubt. I would expect it to be hard to prove innocence after enough evidence was provided to prove guilt.
Note: I am not saying the system always operates according to principles - that's why those 2% get exonerated. I just wouldn't expect the real number of falsely convicted to be much (if any) higher.
Perhaps I phrased it poorly. The standard for proving innocence is raised above a “Preponderance of the evidence” to “Clear and convincing evidence.”
That’s a high standard which if lowered would obviously see more innocent people set free. But we shouldn’t assume there is actually any evidence proving innocence, after all before DNA testing many people who would currently be set free where killed. At best we can estimate who would be set free if we could actually view the past.
If beyond a reasonable doubt is required to convict someone, shouldn't we overturn the conviction as soon as reasonable doubt is introduced? Why would it be desirable that we uphold a conviction that shouldn't have been handed down in the first place if the information was discovered before instead of after the verdict?
So, most estimates suggest in the range of 2-10% of convictions are probably wrongful.