Pollack served 15 years in prison, and, during much of that time, he filed requests for documents related to his prosecution. After extensive research, he found that prosecutors failed to turn over potentially exculpatory evidence, as required by Supreme Court precedent.
Specifically, witnesses who identified Collins as the shooter received deals from the prosecution that diminished their own criminal liability for separate crimes. Some of them were threatend with prosecution if they failed to testify. During the trial, however, prosecutors denied that the witnesses were rewarded for their testimony.
Another witness who testified placed Collins in the area of the shooting. He also said that he made the 911 call reporting the murder. A voice expert, however, testified that the witness was not the person who made the 911 call.
Finally, many of the witnesses admitted to using drugs at the time of the shooting and stated that they barely remember the events of the day or signing documents implicating Collins. One witness stated that Collins received a bad deal.
Prosecutors threatened to retry Collins even if he won the right to a new trial. Following a hearing in federal court that revealed extensive evidence of misconduct, however, prosecutors relented.
Today, Collins works as a paralegal for an attorney who provided assistance during the final stages of his appeals. Predictably, he would like to become a lawyer one day.
The Wall Street Journal article has many more details. It is a very interesting read.