2015 set a record for exonerations in the United States—149 that we know of so far, in 29 states, the District of Columbia, federal courts and Guam. This record continues a trend: the rate of exonerations has been increasing rapidly for several years.
The 149 defendants who were exonerated in 2015 had served on average about 14-and-a-half years in prison. A record 58 defendants who were exonerated in 2015—39% of the total—had been convicted of homicide. Five had been sentenced to death, 19 to life (usually without parole), and the rest to decades in prison.
http://www.law.umich.edu/special/exoneration/Documents/Exonerations_in_2015.pdf