Miscarriages of Justice in Potentially Capital Cases
This paper, published in the Stanford Law Review, looks at the fallibility in the legal system, focusing on capital crimes.
[This paper presents] 350 cases in which defendants convicted of capital or potentially capital crimes in this century, and in many cases sentenced to death, have later been found to be innocent. Our findings prompt us to echo the words of an earlier investigator who noted that the catalogue of erroneous convictions "could be extended, but if what has already been presented fails to convince the reader of the fallibility of human judgment then nothing will."
Twenty-three of these men (none were female) were executed and a further eight died while serving the sentences that had been handed down to them.
Note that life imprisonment typically these days is cheaper than executions for the court systems.