NEW YORK, July 9 (Reuters) - Hector Rivas, imprisoned for 19 years for the 1987 murder of his former girlfriend, on Monday became the first person to convince the federal appeals court in New York that a case as old as his should be re-examined because he may be innocent.

In a case it said was of first impression, a three-judge panel at the 2nd U.S. Circuit Court of Appeals said that although Rivas' petition for release was time-barred, his case could proceed because he had "raised a credible and compelling claim of actual innocence."

The panel sent the case back to District Judge Gary Sharpe in Albany to determine whether Rivas should be freed.

Rivas, 60, was found guilty at trial in March 1993 of murdering Valerie Hill, 28, a pediatric nurse. He was sentenced to 25 years to life in prison.

After his state court appeals were rejected, Rivas filed a federal habeas petition in December 2001. In the petition, he acknowledged that he had missed the one-year deadline to challenge his conviction but asked for an exception because of newly discovered evidence.

Rivas claimed that in 1992, prosecutors in Onondaga County, in a bid to close what had been an unsolved murder, persuaded the local medical examiner to push back the victim's estimated time of death by one day, to Friday, March 27, when Rivas had no alibi.

Monday's 64-page opinion by judges Jose Cabranes, Rosemary Pooler and Robert Sack noted that the 2nd Circuit had until now "resisted deciding" similar cases but that Rivas had raised substantial questions about his actual guilt.

As part of his petition, Rivas brought in an external forensic pathologist who testified that the original medical examiner's "explanation for expanding the possible time of death to include Friday" was "unsound, and perhaps improper," the opinion said.

Rivas' "claim is based on new information not presented to the jury that dramatically undermines the central forensic evidence linking him to the crime of which he was convicted," Cabranes wrote for the panel.

The court relied on a 1995 U.S. Supreme Court case, Schlup v. Delo, which held that in a habeas corpus case where a credible and compelling claim of actual innocence is made, the petition could proceed despite being procedurally barred.

A spokeswoman for the New York State Attorney General's office declined comment on the opinion.

A lawyer for Rivas applauded the ruling.

"Thank God for federal appeals judges who have the courage to stand up and say 'foul,'" said Richard Langone.

The case is Hector Rivas v Brian Fischer, 2nd U.S. Circuit Court of Appeals, No. 10-1300.

For Rivas: Richard Langone of Langone & Associates.

For Fischer: Priscilla Steward, Office of the New York State Attorney General.

(Reporting By Basil Katz)

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