WASHINGTON (CNN) -- A lawyer for a convicted rapist asked the Supreme Court on Monday for a chance to prove his client's innocence with a new DNA test, a request met with skepticism from some justices.

An expert says the Supreme Court is finally going to decide whether convicted prisoners can access DNA.

At issue is whether inmates can use a federal civil rights law to press for advanced DNA testing that was unavailable at the time of their crimes. Forty-four states and the federal government have laws allowing post-conviction access to such evidence, but Alaska is not among them.

"If he succeeds in this case, that doesn't get him outside the prison door," said Justice David Souter. "All it does is get him some evidence to test."

"It is exactly a question of displacing what the states have done because now this question is going to be subject to constitutional law and it's going to be litigated" on a potentially endless stream of claims by convicted criminals, he said.

William Osborne's trial attorney in Anchorage made a strategic decision 15 years ago to forgo additional forensic testing of the evidence in a criminal assault case, believing it would implicate her client. Years later, the Alaska inmate sought access to the state's biological evidence.

Osborne and a co-defendant were convicted in the 1993 rape, beating and shooting of an Anchorage prostitute.

Though the circumstances of only his case are at issue here, the implications could be felt across the country. A high court ruling in favor of the defendant could open all states to something close to mandatory post-conviction DNA testing for older crimes where such evidence is available.

Some states fear a flood of frivolous lawsuits clogging the courts from prisoners whose guilt has already been established.

The Innocence Project, representing Osborne, notes that DNA testing has exonerated 232 wrongly convicted people in the past two decades, including 17 men on death row.

Alaska officials said in their high-court appeal that even if current genetic testing does not show the semen and hair at the crime scene matches Osborne, other evidence remains strong enough to uphold the conviction.

They said that since there was no trial error, Osborne should have made his claim of right to access biological evidence at the trial, not on appeal.

Alaska Assistant Attorney General Kenneth Rosenstein said the defendant has refused to submit an affidavit asserting his innocence.

Justice Antonin Scalia quoted Osborne's own affidavit when making his initial appeal, which said: "I have no doubt whatsoever that retesting of the condom [from the crime scene] will prove once and for all time my guilt or innocence."

"I mean, what is that?" asked Scalia, shaking his head.

"If he doesn't allege his actual innocence," Rosenstein told the court, "then this is really a fishing expedition" because the inmate could be subject to perjury if he declares his innocence, but the tests later confirm his guilt.

Scalia called it "gaming the system."

The Obama administration supports Alaska, and a Justice Department lawyer called Osborne a "poor candidate for relief" because he has twice admitted guilt under oath.

But when Deputy Solicitor General Neal Katyal said Alaska could be buried in a "floodgate" of criminal post-conviction appeals, under a constitutionally established standard for relief, Justice John Paul Stevens pressed him for specifics.

"There are seven [DNA request] cases in this state in the whole of Alaska," Stevens said.

"That's floodgates?" he asked to courtroom laughter.

Osborne's lawyer Peter Neufeld said it was "completely irrational" for the state to put up legal impediments to a basic request for DNA testing.

"That would be terrible if the primary goal of our criminal justice system is that someone who is actually innocent of the crime for which he is serving a sentence can't present evidence that will win him his freedom," he said.

Osborne was found guilty in 1993 of kidnapping and assault. He and a co-defendant were convicted of raping an Anchorage prostitute, then beating her with an ax handle, shooting her in the head and dumping her in a snowbank near the airport, believing her dead.

The victim survived and identified Osborne from photo lineups. He was given 26 years behind bars, with five years suspended.

His co-defendant has continued to implicate Osborne, and the 36-year-old prisoner admitted his guilt in a 2004 parole hearing, though he later said he made the confession only to secure his release.

Initial state forensic testing on a condom and hairs found at the crime scene found the DNA consistent with Osborne's genetic profile, but that one in six African-Americans might share a similar genetic profile.

Osborne's appointed trial counsel declined more sophisticated, independent testing, believing the initial one-in-six rate provided "very good numbers" to make a case for mistaken identity, according to an affidavit submitted in the high court appeal. The trial lawyer was also worried further testing could implicate Osborne.

A federal appeals court ruled in favor of Osborne, saying Alaska was trying to "foreclose" his possible innocence "by its simple refusal to open the evidence locker."

Osborne's legal team said that under a section of the Civil Rights Act of 1871 he has a right to such evidence in the government's possession when making a "free-standing" claim of innocence.

The high court has never before decided what role DNA can play in post-conviction appeals, despite a variety of testing that has been around for more than two decades.

"So finally the Supreme Court, perhaps a bit belatedly, is taking up the issue of what is the standard going to be and how much access should prisoners be given in cases where DNA might prove they're innocent," said Edward Lazarus, a legal analyst and author of "Closed Chambers," a book on the justices. "It might also prove beyond a shadow of a doubt that they're guilty."

Osborne was freed from prison last year, but within months was re-arrested then convicted in December of kidnapping and assault in a home invasion in Anchorage. He is awaiting sentencing on those counts.

The Supreme Court case is District Attorney's Office for the Third Judicial District v. Osborne (08-6). A ruling is expected by late June.

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