The jury began deliberations about midday on Thursday (New Zealand time).
They have spent three full days discussing the evidence behind closed doors at the Kamloops Law Courts, retiring to their sequester in the evening.
Jurors have returned to court twice with questions - to re-listen to testimony from three Crown witnesses and to have British Columbia Supreme Court Justice Ian Meiklem clarify part of his instructions.
Letts-Beckett admitted to having suicidal thoughts in a 2007 diary entry.
The court heard Letts-Beckett went into the water while she and Beckett were on an evening boat ride near Shelter Bay Provincial Park campground.
She was not wearing a life jacket and was not a strong swimmer. In her 90-minute closing submission to the jury, defence lawyer Donna Turko pointed out a lack of physical evidence connecting Beckett to his wife's death.
"No one testified, 'I saw Mr Beckett cause the death of his wife,' nor is there any medical evidence saying so," she said.
"This is purely a circumstantial case."
Ms Turko attempted to poke holes in the Crown's theory on motive, saying that Letts-Beckett handled all of the insurance paperwork in the relationship and that the amount of money in question was only enough to cover outstanding debts.
Crown witnesses lied in court, Ms Turko said, and police deliberately withheld information about how much a jailhouse informant who testified against Beckett was paid.
She also made allegations during the trial about police "trickery" in the investigation. "Some people came to court as more of a witch hunt ... to burn him at the stake," Turko said.
In its closing, the Crown meticulously detailed a number of inconsistencies in Beckett's various statements to police and other witnesses.
Prosecutor Sarah Firestone said the totality of the inconsistencies meant Beckett killed his wife.
"All of his lies demonstrate that he is responsible for getting her in the water and keeping her there until she drowned."
Ms Firestone said "one of the most significant lies" Beckett told was that he used a rock from the shore to sink himself down to Letts-Beckett's body and pull it to shore.
"It defies common sense that a rock is heavy enough to sink with which you can still swim," she said. "The accused is lying to you about finding a rock and doing anything to save Laura. He wasn't trying to save her because he was trying to kill her."
The couple married in 2003. Previous witnesses have described their relationship as a rocky one, though a defence witness - Anita Leigh, a friend of Letts-Beckett - testified the couple acted like "lovebirds."
The Becketts separated in late 2007, but reconciled months later. That year, Letts-Beckett went to police alleging physical abuse on the part of her husband but no charges were laid.
Jury deliberations will resume are to resume. If jurors cannot reach a unanimous decision, a hung jury will be declared and jurors will be selected for a new trial. Kamloops This Week
