As we all know that the American criminal justice system is of urgent concern to average Germans, I pass along this study by Seton Hall Professor D. Michael Risinger, which attempts to provide a scholarly and reliable estimate of the number of innocent people in U.S. prisons:
Using DNA exonerations for capital rape-murders from 1982 through 1989 as a numerator, and a 406-member sample of the 2235 capital sentences imposed during this period, this article shows that 21.45%, or around 479 of those, were cases of capital rape murder. Data supplied by the Innocence Project of Cardozo Law School and newly developed for this article show that only 67% of those cases would be expected to yield usable DNA for analysis. Combining these figures and dividing the numerator by the resulting denominator, a minimum factually wrongful conviction rate for capital rape-murder in the 1980’s emerges: 3.3%.
I haven’t read the entire article, but I can say that this result squares with my gut feeling gained from my personal experience as a (soon-to-be-erstwhile) criminal defense lawyer.