A British sailor allegedly murdered his wife and deliberately sank their catamaran to inherit her estate and end their "marital strife".
Lewis Bennett, from Poole, Dorset, has been charged with murder by the FBI after he was rescued off the coast of Cuba without Isabella Hellmann, the mother of his child.
The newlyweds were sailing towards their US home in May last year when Bennett made an SOS call saying the 41-year-old former estate agent was missing and the vessel was sinking.
Ms Hellmann's body is yet to be found.
Prosecutors in the US have for the first time extensively detailed what they believe to be Bennett's motives.
The British-Australian national is currently serving a seven-month jail term for attempting to smuggle rare stolen coins during the trip
According to prosecutors, Bennett deliberately scuttled the 37ft vessel he was on board with his wife.
Court papers filed this week revealed Ms Hellmann's family bugged her condo in Delray Beach, Florida, to listen to Bennett's conversations because they suspected him in her disappearance.
Prosecutor Benjamin Greenberg asked a Florida judge to admit into evidence conversations with loved ones where Ms Hellmann is said to have discussed rows over a mooted move to Australia, their dire finances and the raising of their daughter.
He argued they show the pair were "consistently" rowing, adding: "With potentially one of the arguments ultimately resulting in the murder of Hellmann."
"Hellmann’s murder would remove the marital strife from the defendant’s life, allow the defendant to live his life as he pleased, and would enable him to inherit money from Hellmann's estate, all of which provide strong circumstantial proof that the defendant had a strong motive to murder Hellmann," he continued.
If Ms Hellmann is presumed dead – as Bennett, 41, has requested – he would inherit her condo and the contents of her bank account.
Prosecutors also alleged she may have discovered he was in possession of the gold and silver coins stolen from his former employer in St Maarten, which could have made her an accomplice in the smuggling crime.
This "potentially led to an intense argument resulting in Hellmann’s murder", Mr Greenberg wrote.
Bennett is due to go on trial in December.