A former Pittsburgh police officer was sentenced to 52 months in federal prison yesterday for possessing improvised explosive devices at his home.

Paul A. Palmer Jr. received a five-month break on the recommended sentence because U.S. District Judge David S. Cercone said he's already been punished to some degree.

Mr. Palmer lost part of his left arm below the elbow in an explosion at his Oakdale trailer in May 2007.

"The biggest victim of this incident was the defendant himself," Judge Cercone said.

North Fayette police officers responding to the scene found Mr. Palmer sitting on a step outside his trailer with burns to his upper chest, singed hair and a severely injured left hand, which was later amputated.

During a search of the home, investigators found a number of components for IEDs, including black powder, cardboard tubes, red phosphorous and a green pyrotechnic fuse that was hidden in the padding of an armchair.

"Paul's use and construction of these explosives were not meant to harm anybody, and he did not harm anyone but himself," said Mr. Palmer's defense attorney, James Wymard.

Some of the explosives found were used by Mr. Palmer to "go out in the woods to blow up pumpkins -- which is a common practice in the area where he lives," Mr. Wymard said.

Mr. Palmer referred to those as "home-made" M-80s.

"I didn't even know the potential damage until this happened," he said. "I never meant to harm anybody."

But Assistant U.S. Attorney Shaun Sweeney disagreed.

"These devices also included metallic BBs," he said. "If you just want to blow something up, there's no need for that ingredient."

During a search of his home, agents also found a large amount of literature from white supremacy groups, in particular the Aryan Nation. There were 15 books and two flags, they wrote. Mr. Palmer also has a number of tattoos consistent with those groups.

He was previously convicted in a road rage incident from 2003 in which he fired a gun at a passing motorist on the Parkway West. He was sentenced to time served plus three years' probation.

Mr. Wymard asked the judge for a lesser sentence, arguing that his client suffered sexual abuse as a child and is mentally ill -- taking five psychiatric medications each day.

At the time of the incident, Mr. Palmer, who had been an officer with Pittsburgh for more than 10 years, had been off-duty for a year with carpal tunnel syndrome. He resigned after his arrest.