An Old Lyme man who carried out a series of armed bank robberies in 2007 and then became a prison informant, helping the state prosecute two murderers, was sentenced Friday to more than six years in prison plus 13 years of special parole.

Kenneth Buckingham, 48, had pleaded guilty to robbing four banks in Centerbrook, Salem and East Lyme and to two cases involving stolen checks.

State police arrested Buckingham and another man, Kevin Smith, in May 2007 after realizing that someone was routinely holding up area banks on Tuesday mornings. The police were keeping a close watch on East Lyme banks on a Tuesday morning when they spotted a car matching witness descriptions.

Hoping for consideration from prosecutors, Buckingham agreed to testify at two murder trials about information he had received while incarcerated with the accused killers.

Last year in New London Superior Court, he testified at the trial of George M. Leniart, who was convicted of raping, strangling and murdering a Montville teenager in 1996. With help from Buckingham and other witnesses, the state convinced a jury that Leniart had killed April Dawn Pennington even though the 15-year-old girl's body has never been found. Leniart, an Uncasville native who had a history of sex offenses, is serving a sentence of life in prison without the possibility of release.

Buckingham also testified at the murder trial of Richard Read in New Britain, where the prosecutor said his testimony helped secure a conviction and a 50-year prison sentence.

At Buckingham's sentencing Friday in New London Superior Court, prosecutor Paul J. Narducci said the state had not made any promises to Buckingham before his testimony. Narducci said Buckingham had committed serious crimes, but that given the circumstances the 75-month sentence is reasonable. During the 13 years he will be on special parole, Buckingham could be sent back to prison with no further court hearings if he violates the conditions of his release.

Defense attorney Jeremiah Donovan said Buckingham served in the Marines, specializing in a dangerous assignment - reconnaissance - and was deployed to Lebanon and Grenada. He was honorably discharged, Donovan said.

Judge Patrick J. Clifford said Buckingham is a dangerous person and told him, "I doubt you came forward to testify in two murder cases out of the goodness of your heart. You had something to offer, and you got a benefit. If you didn't do that, this sentence could be twice as long."

Buckingham said he didn't go to the state with the jailhouse information.

"They came to me twice," he said.

In the Read case, investigators approached Buckingham after state Department of Correction officials intercepted a letter he wrote to his then-fiancee about the case. Investigators who had been keeping tabs on Leniart, a longtime suspect in the Pennington murder, sought out Buckingham after learning the two men had been housed together in prison.

k.florin@theday.com