Two Baltimore men in prison for murder have raised questions about their convictions, which public defenders say could be answered through genetic evidence that prosecutors are refusing to allow to be tested.

Based on DNA test results, a judge this week ordered a new trial for Robert C. Griffin, a city man convicted in 1986 of murdering a 20-year-old woman. Public defenders say that decision highlights the need to test old DNA whenever possible, but they say they have been hindered by city prosecutors who oppose reopening the cases.

"The bottom line is, if they are so confident about their convictions, why not let us test the evidence?" said Michele Nethercott, who heads the state public defender's Innocence Project.

Nethercott said her group, which is based in Baltimore and evaluates possible wrongful convictions throughout the state, has received cooperation in every other state's attorney's office they've approached. But in Baltimore, "they fight everything tooth and nail," Nethercott said.

The city state's attorney's office policy on post-conviction motions is to make the defense seek a court order for DNA testing, said spokeswoman Margaret T. Burns. "It's our job to protect the state's case to ensure that justice is served," she said.

Prosecutors staunchly opposed DNA testing in two murder cases in which public defenders have recently filed motions.

One case involves one of two men convicted in 1988 of raping and stabbing to death a woman in her bed. The state medical examiner's office prepared a slide of sperm that was collected from the victim. In the other case, a man was convicted in 2003 of first-degree murder in a shooting death. The Police Department swabbed skin cells from the trigger of the murder weapon.

Genetic material has been preserved in both cases but never tested.

Advances in DNA testing mean that genetic material - such as hair, skin cells, blood and sperm - saved from crime scenes and victims can sometimes shed new light on cases. The material is usually in the possession of local police departments or the state medical examiner's office, and it takes either the consent of prosecutors or a court order to release it for testing.

DNA testing has led to at least six overturned convictions in Maryland, although Griffin, who won a new trial after a hearing Monday, is the first in Baltimore City.

Griffin, 71, has not been exonerated in the killing of Annie Cruse in 1985, but his attorney, Suzanne Drouet, of the Innocence Project, said she is hopeful that the new evidence will clear his name in a retrial, for which a date has not been set. Nethercott and Drouet called it a "fluke" that they were able to test a slide of sperm the state medical examiner's office retained.

The prosecutor in Griffin's case, who was leaving the state's attorney's office, agreed to release the evidence. Since then, prosecutors have opposed similar requests for testing in other Baltimore cases.

In one, James Thompson was convicted by a Baltimore jury in 1988 of raping and murdering Colleen Williar, 24, in the upstairs bedroom of her O'Donnell Heights rowhouse.

Thompson was originally identified by police as a witness, and he testified in the murder trial of James Owens. During the Owens trial, Thompson said he was present during the rape and murder, and he was then charged in the case. Thompson later changed his story to say he wasn't at the scene and had nothing to do with the crime.

Both men claimed during their trials that they are innocent. Drouet now represents Thompson. She said a DNA test on sperm from the victim would lend clarity to a confusing case.

The DNA could match either Thompson or Owens, showing that the state prosecuted the right men. It could match neither of them, meaning that the wrong men might be in prison.

Or, as happens in the majority of cases with old biological evidence, the tests could come back inconclusive.

In his motion opposing the defense request for post-conviction DNA testing in the Thompson case, Assistant State's Attorney Mark P. Cohen stated that Thompson's confession to the crime at Owens' trial and physical evidence prove that he's guilty even if sperm from the victim does not match him.

In August, Baltimore Circuit Judge Kaye Allison denied the defense petition for DNA testing, citing questions about the reliability of DNA as her reason. Drouet is appealing Allison's decision.

The Innocence Project has also taken up a more recent city murder case.

Donte Gregg was convicted in 2003 of first-degree murder and handgun charges. Nethercott, Gregg's attorney, said her client claims that another man in his vehicle jumped out, fired the fatal shots and got back inside, forcing him to drive away.

When police caught up with the vehicle, which belonged to Gregg, they found the murder weapon in a wheel well, according to prosecutors. Police swabbed skin cells from the trigger.

Believing they already had enough evidence for a successful prosecution, police and prosecutors did not test the skin cells. "We didn't need them," Burns said. But Assistant State's Attorney Matthew Fraling did tell defense attorney Howard L. Cardin about the cells. He did not conduct a test.

Cardin filed a petition for post-conviction review, but Nethercott - who has since taken over the case - has withdrawn that motion and is filing one for a new trial.

Fraling, who opposed Cardin's request and will oppose Nethercott's, said the defense knew about the skin cells and should have had them tested before the original trial. He also said in the motion that even if the skin cells are not Gregg's, that doesn't prove he didn't fire the weapon.

Prosecutors said other evidence in the case, from gunshot residue on Gregg's hands to a witness who described Gregg's clothing, prove the right person has been convicted.

But Nethercott said finding out whose skin cells are on the trigger could corroborate Gregg's version of what happened, that the other man in his vehicle fired the shots.

"I don't understand why the practice [of city prosecutors] is to fight, fight, fight," Nethercott said.

Drouet added: "It seems like once they have a body convicted of a crime, they hang onto it no matter what."

Burns said prosecutors would agree to DNA testing in an old case if defense attorneys could show a clear-cut example of genetic material being used at a trial to wrongly convict someone.

"But in these cases we're talking about now," Burns said, "the DNA has very little relevance to the facts of the case."

Other state's attorney's offices in Maryland take a different approach. In Baltimore County, Nethercott and Deputy State's Attorney Stephen Bailey have developed a policy of cooperation.

Bailey said county prosecutors try to handle post-conviction requests for DNA testing outside of the courtroom.

"We begin with the premise that if there's evidence out there that shows someone was wrongfully incarcerated, we want to make sure that evidence is tested," Bailey said. "The goal is to do justice, not to get convictions."