A 75-year-old California man was charged with the chilling 1978 murder of a young British couple who had been sailing on his boat in the Caribbean Sea.

Silas Duane Boston allegedly beat and bound Christopher Farmer and his girlfriend Peta Frampton, attaching weights to their bindings and covering their heads with plastic bags before dumping them alive overboard in a fit of rage.

The murders took place between June and July 1978 and their corpses were found on about July 8 floating at sea off the coast of Guatemala.

A probe into their murders went cold even though Boston was interviewed a number of times by investigators about disappearances.

The case, worthy of a crime novel or horror movie, was relaunched thanks to an investigation into the 1968 disappearance of Boston's former wife, Mary Lou Boston.

Boston allegedly also killed her, according to the criminal complaint. 

He was arrested last week at a convalescent home in the town of Paradise, in northern California.

He appeared in federal court on Thursday in a wheelchair and entered a not guilty plea.

Farmer and Frampton, both from Manchester, England, at the time of their murders, were fresh university graduates in their mid-20s -- he from medical school and she from law school -- and had decided to take a year off to travel.

They first went to Australia before setting off to the Americas, and throughout their journey had remained in close contact with their families.

They informed their parents in a letter that they had met Boston while in Belize and they had chartered his boat to take them to Mexico.

Frampton in a letter dated June 29 indicated it was not always smooth sailing on the boat as Boston's two young sons, who were also on board, squabbled frequently and he had a short temper.

Their families became concerned when they failed to hear from them for several weeks and alerted authorities who eventually connected two bodies found off the coast of Guatemala to the couple.

Boston's two sons, Russell and Vince, have implicated him in the brutal killings, according to the criminal complaint.

Vince, who was 13 at the time, told investigators that he had seen his father beat Farmer with a billy club and then attempt to stab him with a fillet knife that broke.

- Chilling details -

He said Boston bound both of his victims before dumping them overboard.

Boston allegedly later bragged about the killings, telling a former friend how he had tied the couple, put bags over their heads and dumped them overboard.

"Boston said the female on the boat heard the splash of the male victim entering the water and started calling her boyfriend's name and after a couple of minutes Boston threw the female into the water," the friend told investigators, according to the complaint.

Both Boston's sons and the friend had apparently failed to come forward out of fear he would come after them.

"Russell stated he recalls Boston being intoxicated after the murders of Farmer and Frampton and he threatened to kill the boys," the complaint states.

Both Russell and Vincent also told investigators that their father had bragged about killing their mother and several other people.

He allegedly took his wife to an undisclosed location and then ordered her to run before shooting her.

Boston faces life in prison if convicted in the murders of Frampton and Farmer.

Federal prosecutor Phillip Talbert on Thursday said the persistent efforts of investigators, notably the FBI and the police in Sacramento, had allowed the case to go forward.

"Nothing would have happened if the Sacramento Police Department had not thought to consult with this office about what could be done with a 38-year-old homicide in the Caribbean sea," he said.

Source: AFP