A man has been charged with murdering two Manchester graduates as they travelled the world nearly 40 years ago.
Former boat skipper Silas Duane Boston, 75, is accused of tying up two young passengers before pushing them overboard attached to heavy machine parts off the coast of Guatemala in Central America in 1978.
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The bodies of medicine graduate Christopher Farmer, 25, and law graduate Peta Frampton, 24, both from Greater Manchester, were discovered 200 metres from the coast near Punta De Manabique on July 8, 1978.
The original investigation by officials in the US and the UK had come to nothing until the families begged Greater Manchester Police's cold case unit to revisit the deaths last year.
It led to GMP contacting the retired detective who had investigated the original case, who handed over records of the case which he had kept in his garden shed.
US detectives were alerted and found Boston's two sons - long estranged from their American father and each other.
Court papers lodged in California show both claim they witnessed their father pushing the young couple from the boat, allegedly in a fit of anger because Mr Farmer admonished the skipper for attacking his own son.
Last week Mr Boston was arrested at his home in Paradise, California, and he now faces a trial in the US.
Mr Farmer and his girlfriend Ms Frampton had travelled to Australia - where Mr Farmer had briefly worked as a doctor in Brisbane - and to the Americas as part of a round-the-world trip to celebrate their graduations.
The pair wrote back to their parents frequently and reported they had met an American called 'Dwayne' who had offered to take them from Belize to Mexico.
In Ms Frampton's final letter, postmarked July 18, 1978, she ends: "Enough of the future. I don't think there's any more news - nothing much happens on a boat. Lots of love Peta."
Two badly-decomposed bodies of a man and a woman were later found floating in the sea about 200 metres from the beach off Punta De Manabique.
The bodies of Christopher Farmer, centre, and his girlfriend Peta Frampton (not pictured) were discovered with their ankles bound (MEN)
Volunteer firefighters, or 'bomberos', recovered the bodies, noting the male had ankles bound and the hands were tied behind the back.
The body had been attached to a 'shock block', part of a car engine which can be used as ballast, by a 15m length of string.
There was a 'bullet hole in the right leg and signs of torture', according to the English translation of the bomberos' report quoted in the US court documentation.
The body of the woman had also been bound and was also attached to a car engine part which was resting on the bottom of the sea.
Both bodies were buried in Guatemala but only identified after they were exhumed a year following the deaths. They were finally identified using dental records.
Court documents showed the UK consulate general in San Francisco managed to speak to Mr Boston, the skipper of a boat named Justin B on which the pair had sailed, by phone and the American claimed his two passengers had disembarked because his boat had required repairs.
Mr Farmer's father Charles also managed to raise Mr Boston in a trans-Atlantic phone call and, according to US court documents, the skipper said he didn't know what had happened to the couple and said: "Let me know if you hear anything about them."
But Mr Boston's own sons now say they witnessed their father murder the couple.
Vince Boston, aged 13 at the time, said his father 'would become very violent when he drank alcohol' and described how his dad tried to hit Mr Farmer but missed and ended up in the water after the latter had told Mr Boston to leave his younger son Russell, 12, alone, according to the criminal complaint lodged in the US.
Vince Boston alleged his father repeatedly struck Mr Farmer to the back of the head with a wooden 'billy club' as the young doctor is said to have cried: "What's your game? What's your game?"
When his girlfriend emerged from the galley, Mr Boston is alleged to have threatened to shoot her with a spear gun.
Mr Boston tried to stab the medic in the chest with a fillet knife but the blade broke and his father then bound his two passengers with ropes, according to Vince Boston.
The following morning he is said to have told his two passengers he intended to tie them to a tree so they could be discovered and he could escape.
He also demanded the pair sign over their traveller's cheques to him, it is alleged.
The skipper then 'hog tied' his passengers at the rear of the boat and put plastic bags over their heads before pushing first Mr Farmer and then Ms Frampton overboard, followed closely by the machine parts to which they were attached by a length of rope, it is claimed.
"Boston looked at his watch and after a three or four minutes stated 'OK they are dead now'," according to the criminal complaint file.
Mr Boston's younger son Russell, in his own statement referred to in the US court documents, said his father had been 'angry' after Mr Farmer had 'pushed (him) overboard'.
Mr Farmer had jumped to the defence of the youngster and asked his father to 'leave him alone' after the skipper had been 'yelling and punching Russell Boston', according to the US court documents.
Russell Boston also alleged his father had attacked the young medic from behind with 'an antique billy club' and then tried to stab him with a fillet knife.
He described how the skipper sailed away and after a few hours of silence allegedly told his sons: "You know, I had to do that. They didn't give me a choice."
Russell Boston also alleged his father steamed open letters Peta Frampton had written and then posted them to ensure the families believed the couple were 'still alive'.
He recalled his father 'being intoxicated after the murders' and claimed he also threatened to kill his own sons.
Mr Boston admitted to his sons to killing others including their mother, according to the documents, and is alleged to have told his kids: "If there is a heaven, they can find their mother."
The US court papers also outline how Mr Boston told a friend with whom he had travelled through Mexico in the 1990s that he had 'committed a number of murders'.
The former friend alleged Mr Boston had claimed he had thrown a couple from his boat and claimed 'it was funny' that he had heard the woman's 'screams through the bubbles that came up while she was drowning'.
A spokeswoman for GMP said: "Greater Manchester Police Cold Case Unit have been working with the families of Christopher Farmer and Peta Frampton for over a year since relatives asked us to reinvestigate these tragic events.
"Since that time, we have worked closely with Interpol, Sacramento Police Department, the FBI and the U.S. District Attorney's office.
This inter-agency cooperation has led to the two murder indictments being issued by the U.S Grand Jury.
"The families of both Chris and Peta now await the outcome of a trial and would ask for privacy in the meantime."