A sailor murdered his wife and deliberately sank their catamaran to inherit her legacy and put an end to their "marital quarrel," claimed prosecutors.
Lewis Bennett, from Poole, Dorset, smuggled rare stolen coins when he was rescued only off the coast of Cuba without Isabella Hellmann, the mother of his child.
Public prosecutors in the US have for the first time described in detail what they consider to be Bennett's motives after the FBI had promised him murder.
Court papers filed this week also revealed Ms. Hellmann's family tapped her apartment in Delray Beach, Florida, to listen to Bennett's conversations because she suspected him in her disappearance.
The newlyweds were on their way to their home in the US in May of last year when Bennett made an SOS call in which the 41-year-old former broker was missing and the ship sank.
Prosecutor Benjamin Greenberg has asked a judge from Florida to inspect evidence from loved ones where Mrs. Hellmann has reportedly argued about a motivated move to Australia, their troubled finances, and raising their daughter.
He claimed that they showed that the couple was rowing "consistently" and added: "With possibly one of the arguments that ultimately resulted in the murder of Hellmann."
"Hellmann's murder would remove the marital quarrel from the suspect's life, allow the defendant to live his life as he wished, and allow him to inherit money from Hellmann's inheritance, all of which are strong indirect evidence provides that the suspect had a strong motive for murder Hellmann, "he continued.
If Mrs. Hellmann is supposed to be dead-as Bennett, 41, asked-he would inherit her flat and the contents of her bank account.
Prosecutors also claimed that they might have discovered that he was in possession of the gold and silver coins that had been stolen from his former employer on St. Maarten, making her complicit in smuggling crime.
This "possibly led to an intense argument that led to Hellmann's murder," wrote Greenberg.
The FBI accused the British-Australian of deliberately pillaging the 37ft ship and he served seven months imprisonment after admission of the coins worth 38,480 dollars (£ 29,450).
Mrs Hellmann's body has not yet been found.
Bennett has to go on the road in December on charges of second-degree murder.