>Certainly the wrongly convicted constitute an immeasurably small
>percentage.
No. Anywhere from 2 to 10% in the US, which is small, but hardly insignificant, let alone immeasurably small. In the US, this equates to tens of thousands of persons. Higher if you count the people who did something but just not the thing for which they were convicted (e.g., some lesser offense but pleaded guilty or had a poor defense--the kind of defense most poor people unsurprisingly receive, most especially in the incarceration-happy Southern states with conviction-prone, state-predisposed juries and no public defender system). Most of these will never be discovered because 99% of prisoners have no means to obtain post-conviction counsel to investigate their innocence, and many of the wrongly convicted never even had a trial (which makes proving innocence post-conviction 1000 times harder in the absence of DNA evidence, which the overwhelming majority of criminal cases lack).