The decision may have limited impact because the federal government and 47 states already have laws that allow convicts some access to genetic evidence. Testing has led to the exoneration of at least 232 people who had been found guilty of murder, rape and other violent crimes.

The court ruled 5-4, with its conservative justices in the majority, against an Alaska man who was convicted in a brutal attack on a prostitute 16 years ago.

William Osborne won a federal appeals court ruling granting him access to a blue condom that was used during the attack. Osborne argued that testing its contents would firmly establish his innocence or guilt.

In parole proceedings, however, Osborne has admitted his guilt in a separate bid for release from prison.

The high court reversed the ruling by the 9th U.S. Circuit Court of Appeals in San Francisco. States already are dealing with the challenges and opportunities presented by advances in genetic testing, Chief Justice John Roberts said in his majority opinion.