WASHINGTON - Prisoners have no constitutional right to DNA testing after their conviction, a split Supreme Court ruled yesterday, even though the technology provides an "unparalleled ability both to exonerate the wrongly convicted and to identify the guilty."

In the court's first examination of how to treat the rapidly evolving field of biological testing, Chief Justice John G. Roberts Jr. wrote for the 5-4 majority that it was up to the states and Congress to decide who has a right to testing that might prove innocence long after conviction.

The "challenges DNA technology poses to our criminal justice systems and our traditional notions of finality" are better left to elected officials than federal judges, he wrote.

"To suddenly constitutionalize this area would short-circuit what looks to be a prompt and considered legislative response," he wrote. He was joined by Justices Antonin Scalia, Anthony M. Kennedy, Clarence Thomas, and Samuel A. Alito Jr.

The case was one of the most anticipated of the term, given the revolutionary role DNA testing has played in modern criminal proceedings. The Innocence Project, a group representing those who say they have been wrongfully convicted, said DNA testing had exonerated 240 people nationwide, at least 17 of whom had received the death penalty.

Dissenting justices, led by John Paul Stevens, said the right to post-conviction DNA testing should not depend on the widely varying laws enacted by the states.

Allowing a prisoner to test DNA evidence at his own expense would "ascertain the truth once and for all," Stevens wrote. Justices David H. Souter, Ruth Bader Ginsburg, and Stephen G. Breyer also dissented.

The case, District Attorney's Office v. Osborne, came from Alaska, one of three states, along with Massachusetts and Oklahoma, without a law allowing post-conviction access to biological evidence.

William Osborne was convicted of the 1993 rape and assault of a prostitute in a secluded area near Anchorage International Airport. He wanted to pay for a more discerning test of semen found in a condom at the crime scene - a test prosecutors agreed would almost definitively prove his guilt or innocence. Prosecutors refused to allow the test, and Alaska courts agreed he did not qualify under the procedures they had established.

Osborne appealed, and the U.S. Court of Appeals for the Ninth Circuit in San Francisco recognized a right to such testing under the Constitution's Due Process Clause.

But Roberts said that was wrongly decided.

"A criminal defendant proved guilty after a fair trial does not have the same liberty interests as a free man," he wrote, and thus states have more "flexibility" in deciding procedures for post-conviction relief.

Prosecutors had told the court that Osborne was not a good cause for those worried about the wrongly convicted. He was identified as the woman's attacker by not just her but also by an accomplice. Osborne has both professed his innocence and confessed to the crime. He is back in prison on an armed-invasion conviction.

Attorney General Eric H. Holder Jr., in a statement, said of the ruling: "The court merely spoke about what is constitutional, not what is good policy. And there is a fundamental difference.. . . DNA testing helps ensure that justice is done. For that reason, this administration believes that defendants should be permitted access to DNA evidence in a range of circumstances."

Also yesterday, the court, voting 5-4, made it harder for workers to win age-discrimination suits, overturning a $47,000 award to a demoted employee in his mid-50s.

The justices said workers must show that age discrimination was the cause of a demotion or other adverse employment decision, not just one of several factors that played a role.

The ruling in Gross v. FBL Financial Services Inc. means workers must meet a tougher standard under the Age Discrimination in Employment Act than they do when alleging race or gender discrimination under a different law, known as Title VII.

Thomas, writing for the majority, said workers had to show that the employer's action would not have occurred without age bias. He was joined by Roberts, Scalia, Kennedy, and Alito.

In dissent, Stevens called the ruling "unnecessary lawmaking" that went beyond the issues the court agreed to consider in the case. Breyer, Souter, and Ginsburg also dissented.

Read the justices' opinions in the

Osborne case via http://go.philly.com/