State Sen. Robert Regola III went on the offensive yesterday, saying his decision to switch political parties was the reason prosecutors charged him with a series of crimes in the suicide of a neighbor boy.

"It was political. I'm the first Republican senator representing Westmoreland County in 72 years," Mr. Regola said during a wide-ranging interview in his campaign office in Greensburg.

Democratic District Attorney John Peck, in an earlier interview, said law, not politics, was behind his decision to prosecute Mr. Regola. Mr. Peck said he pursued the case because he thought he had a solid basis for bringing two felony and four misdemeanor charges against the senator.

A jury acquitted Mr. Regola a week ago of perjury, providing a firearm to a minor, reckless endangerment and three counts of false swearing. All the charges were related to the death in July 2006 of 14-year-old Louis Farrell. The Westmoreland County coroner ruled that Louis shot himself with the senator's 9 mm pistol.

"I don't know what happened or why he would do such a thing," Mr. Regola said of Louis taking his gun.

He said he thinks of Louis each day and sympathizes with his parents, whose pain must be immense. Louis' parents remain his next-door neighbors, but the families do not speak to each other. Mr. Regola said he wanted to repair the friendship they once had but said he had not contacted the Farrells since his acquittal.

The prosecution's theory of the case was that Mr. Regola gave the 9 mm pistol to his son, Bobby, then 14, as a Christmas present in 2003. Ownership records showed that Mr. Regola bought the gun on Dec. 7, 2003.

Mr. Peck said Louis knew about the pistol because it actually belonged to Bobby Regola, who kept it in his room.

At trial, evidence that Mr. Regola provided the pistol to his son was brought forth mainly through Mr. Regola's estranged brother-in-law. But two jurors said yesterday they did not find the prosecution's case compelling.

Juror Daniel Giannetti said a clear majority of the 12 jurors wanted to acquit Mr. Regola from the beginning of their deliberations.

"There wasn't enough tangible evidence brought to the table to convict him," said Mr. Giannetti, at 28 the youngest member of the jury.

Another juror, Teresa Lemmon, said police work in the case was substandard and proof against Mr. Regola was lacking.

Two state troopers who alleged perjury by the senator failed to take and maintain good notes during their investigation, she said. Police said Mr. Regola admitted to them that the pistol was kept in Bobby Regola's room, but changed his story when he testified under oath at a coroner's inquest.

Mrs. Lemmon said one trooper's admission that he did not even have a notebook when he interviewed Mr. Regola left her unimpressed with the state's case.

"I didn't see tangible evidence of perjury. As for the gun, I don't think he did anything wrong," she said of the senator.

Mr. Regola, 45, used to be a Democrat. He switched to the Republican Party and won his Senate seat in 2004, ousting a two-term Democrat.

This time, Democrats have nominated Anthony Bompiani, 55, a chiropractor and former Hempfield school board member, to oppose him in the November election.

Though Mr. Regola won his criminal trial, his legal troubles may not be over. Jon Perry, an attorney for the Farrells, said the family intends to file a wrongful death lawsuit against Mr. Regola as soon as today.