MARBLEHEAD -- For Harry Christensen, the unsolved 1950 murder of Beryl Atherton has become a hobby. Sometimes, at night, he'll pull out his folder and ponder the evidence.
About three times a year, the attorney and Marblehead selectman gives a presentation to local groups about the murder of the 47-year-old, single schoolteacher. It is such a popular program that the Marblehead Chamber of Commerce created an auction item from it.
On Oct. 21, a package that included dinner for eight at the Harborlight Inn followed by a presentation from Christensen sold for $550 at the chamber's annual auction.
''Out of 200 auction items, that was my favorite one, because it's so unique," said Leslie Gould, executive director of the chamber. The lure, she thinks, is the mixture of local history with the suspense of a crime still unsolved.
''Who hasn't watched 'Unsolved Mysteries' and been completely riveted?" she asked.
Christensen, whose late father was a member of the Marblehead police, was 4 years old when the murder occurred. He first wrote about it for a college class, when he was allowed access to the police reports by the late Clemons Rogers, an investigator on the case.
He maintained an interest, and in 2002 made his presentation for the first time to the Marblehead Historical Society.
''It's fantastic," said Joel Gleason, who saw Christensen's presentation to the Marblehead Rotary Club last year. Gleason was 7 years old in 1950. ''[Christensen] gives the details without getting gruesome or gory, enough to make it quite fascinating."
In his presentation, Christensen lays out details of the murder, which stunned the town in an era when residents left their doors unlocked at night. According to Globe accounts from the time period, the body of the Glover School teacher was discovered by milkman Kenneth Phillips on Mon., Nov. 27, at her Sewall Street home. Police theorized that she had been killed during a blackout the previous Saturday night. The woman's throat was slashed six times.
Among the details Christensen shares is that there was a great deal of blood on the scene but no footprints, and that investigators found a wet dish cloth on the sink, indicating that somebody went back into the house and cleaned it up after the attack. There was no money missing that police could account for, but there was a blood stain on the pillow upstairs, and indications that ''someone was looking for something," Christensen said, ''something of value to that person."
Christensen has a suspect, whose name he doesn't reveal in his presentation.
He has shared it, with supporting information, in a safe place to be delivered to Marblehead police in the event of his death.
Christensen and Police Chief James Carney have discussed the case, and Carney has said that he will arrange a meeting with State Police to follow up on Christensen's theory. Christensen would like to see the State Police file, and would like to see the police test his theories with DNA evidence, but he's been reluctant about using his position as a selectman to influence the investigation.
Carney said that police were interested in ''anything substantial" Christensen had discovered.
Christensen said his hobby has come with some unintended consequences.
''When it's late at night and I hear a bump in the night, that can be scary, too," Christensen said.