PITTSBURGH, Pennsylvania - March 8, 2010 - A man says police bullied him into saying he witnessed a murder, and now, he tells Team 4 that he never saw that fatal shooting.

Team 4 investigator Paul Van Osdol reported that Eric Boyd says he agreed to testify after police made threats about his and his family's safety.

Boyd is the only witness prosecutors have, but he says he cannot testify about a crime he never saw.

Pittsburgh police say Darrel Nelson was shot 10 times in a hallway inside a building at Bedford Dwellings in the Hill District on April 17, 2008.

Police charged two men with the killing - Justin Boyd, 17, and Robert Burks, 25. The charges were based on the testimony of Eric Boyd, who is Justin Boyd's cousin.

Eric Boyd says he testified only because a police officer threatened him that "basically, if I don't cooperate with this investigation, my friends and family and everything I love would be in harm's way. It would disappear."

So Eric Boyd testified at the preliminary hearing and went into the witness protection program, moving outside the city.

Eric Boyd doesn't deny he was at Bedford Dwellings at the time of the murder, but the problem for prosecutors is that the shooting occurred all the way down at the end of the street and around the corner, six buildings away from the building where he says he was at the time.

"If I have to testify, I will testify I was at Bedford Dwellings. I did not see a shooting," Eric Boyd told Van Osdol.

Eric Boyd said the same thing to the district attorney's office, but he says they're still forcing him to testify in the case.

University of Pittsburgh law professor John Burkoff says that happens frequently, and it's not easy for prosecutors.

"Most of the people who are eyewitnesses to criminal activity are not nuns and priests, and people who we would think would be mostly telling the truth," Burkoff said.

But Eric Boyd said he is telling the truth - now.

"I'm not willing to testify to try to put someone away for life for something they may not have done," he said.

Justin Boyd's lawyer, Chris Patarini, said the DA's office informed him when Eric Boyd changed his story. Patarini said prosecutors have no case without Eric Boyd's testimony.

Mike Manko, a spokesman for the DA's office, would only say to Team 4 that Eric Boyd will be getting a subpoena for the upcoming trial.

Pittsburgh police had no comment, citing the pending charges.