BUFFALO, N.Y. - The U.S. Supreme Court has rejected a petition to review the murder case of an anti-abortion extremist who is also suspected in the shootings of three Canadian doctors.

James Charles Kopp claims his constitutional rights were violated during the state and federal trials that sent him to prison for life for the sniper-style slaying of an American abortion provider.

The U.S. justices on Monday denied Kopp's petition to review the lower court records. The court gets around 8,000 such requests every year and accepts fewer than 150.

"We're very grateful to the justices for the opportunity to be heard," attorney Arthur Lawrence Washburn Jr. said by phone after speaking with Kopp on Tuesday.

The longtime anti-abortion attorney said he met Kopp, 58, when Kopp was involved in the Operation Rescue movement years ago.

"He's in good spirits," Washburn said from his Vermont home. "He's a very centred person."

It was the third time that Kopp, nicknamed "Atomic Dog" among radicals in the anti-abortion movement, had sought intervention by the nation's highest court since the 1998 shooting of Dr. Barnett Slepian in the kitchen of his suburban Buffalo home.

Kopp separately appealed his 2003 state second-degree murder conviction and his 2007 federal conviction for violating the Freedom of Access to Clinic Entrances Act by killing an abortion provider and of using a scope-equipped military assault rifle in a violent crime.

The most recent petition combined the cases because of overlapping concerns surrounding a conflict of interest by his attorney. The state and federal issues were first presented together before the U.S. Court of Appeals for the 2nd Circuit, which ruled Kopp did not prove his rights had been denied.

Kopp's attorney at his state trial, Bruce Barket, was barred from representing him at his federal trial after a federal judge deemed Barket was conflicted because he had simultaneously defended a couple charged with helping Kopp evade capture after the shooting.

The federal court did, however, allow a confession that Kopp said Barket prompted during the state proceedings to be used as part of the federal case.

Washburn had urged the U.S. Supreme Court to consider the case as a way to clarify whether the Constitution permits evidence generated amid a conflict of interest to be used to convict a defendant, something he said was a "critically important and developing area of jurisprudence."

Kopp, who has maintained he was only trying to wound Slepian to prevent abortions, is suspected in the nonfatal shootings of four other doctors, three in Canada and one in Rochester, between 1994 and 1997.

He is charged with attempted murder in one of those cases — the 1995 wounding of Dr. Hugh Short in Ancaster, Ont.

Although Canadian authorities have expressed interest in prosecuting Kopp, U.S. authorities have said he would have to finish his U.S. sentences first.

Kopp is in federal prison in Canaan, Pa., where he is serving a sentence of 25 years to life on the murder conviction and life in prison plus 10 years on the federal charges.

News from © The Associated Press, 2013