Report finds record number of US exonerations in 2015

The registry is a project of the University of Michigan Law School and has documented more than 1,730 such cases in the U.S.

Since 2011, the annual number of exonerations has more than doubled and there are now an average of nearly three exonerations a week, said Samuel Gross, a University of Michigan law professor and registry editor.

Homicides and sex crimes made up nearly half of all exonerations in the U.S. According to the registry, a record 58 defendants who were exonerated in 2015 had been convicted of homicide, with five having received death sentences and 19 having been sentenced to life in prison.

The three men who were convicted had their arson and murder convictions overturned in December after Thompson's office was able to cast doubt on the fire science that helped convict the men.

Inger Chandler, chief of the conviction review section with the Harris County District Attorney's Office, said her office has since changed its policies and no longer allows pleas in drug cases until a lab report is completed.