The son of John Carlin III, convicted along with Mechele Linehan in a 1996 murder, is suing the Alaska Department of Corrections for his father's brutal prison death.

The younger Carlin says his father should have been protected by prison staff after other inmates attacked him on two separate occasions, according to the lawsuit recently filed in Anchorage Superior Court. The third attack in October 2008 was the final one that killed the 51-year-old former New Jersey steelworker who was serving a 99-year-sentence for murder.

Alaska State Troopers investigated the beating but more than a year has passed and no one has been charged. Troopers spokeswoman Megan Peters said the case is still being worked. Parts of the investigation, like lab results, have not been completed and are delaying the process.

Carlin was convicted in 2007 for the murder of his house guest Kent Leppink. Prosecutors say Carlin and his one-time fiance, Linehan, conspired to kill Leppink, a 36-year-old commercial fisherman, for a $1 million life insurance policy payout. Leppink changed the policy before he died, removing Linehan as a beneficiary.

Linehan was convicted in a separate trial but the Alaska Court of Appeals overturned her conviction two weeks ago. Carlin also said he was innocent and was in the process of appealing. Because he died before he could complete his appeal, the appellate court set aside his conviction. But state prosecutors have asked the Alaska Supreme Court to reinstate Carlin's conviction.

Carlin IV is seeking at least $500,000 in damages.

"Due to the repeated nature of the assaults and Carlin's pleas for help, the officers and/or employees and/or agents of defendants knew or should have known of the danger to Carlin's personal safety," the lawsuit says. No inmates were named as defendants.

A Corrections spokesman said the department would not comment because of the ongoing litigation.

Donald Joseph, an inmate at the Spring Creek prison in Seward with Carlin and who admitted taking part in the first beating, said that he had wanted to teach the new prisoner a lesson. Carlin had apparently taken control of the television when two other people were watching it. Joseph has denied having anything to do with the final, fatal assault a month later.

After the first attack, Carlin was given medical attention, then separated from the other prisoners, according to prison records. When Carlin was released to the general population, inmates beat him again.

The lawsuit charges that Carlin was unsuccessful in his pleas to prison officials that he be separated from the others or moved to another prison.

Carlin IV, now 31, is the only surviving heir to his father. He was a key witness for the prosecution in the trials of his father and Linehan. He testified that he saw his father wash a handgun in the days after the murder. The younger Carlin, though, has said that he doesn't know who killed Leppink and doubts it was his father.

Monday is the deadline for state prosecutors to decide if they are going to drop charges against Linehan or opt for another trial. She is at the state's female prison, Hiland Mountain, in Eagle River.

Find Megan Holland online at adn.com/contact/mholland or call 257-4343.