Beckett, meanwhile, suggested to jurors Letts-Beckett was suicidal prior to her death after suffering for years from depression brought about by a childhood rape by a family friend. Letts-Beckett admitted to having suicidal thoughts in a 2007 diary entry.
Court has 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. Imagine if you were found guilty of murder simply because you were present for the demise of your spouse. While it appears to have been enough to have charged Mr. Beckett, that does not mean he is guilty. ... In this case, there isn't a smoking gun."
Turko attempted to poke holes in the Crown's theory on motive, saying 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.
"The Crown wants you to find Mr Beckett guilty because they just don't know," Turko said.
"This is not proof beyond a reasonable doubt because you just don't know."
A Crown witness lied in court, Turko said, and police deliberately withheld information about how much a jailhouse informant who testified against Beckett was paid.
"Some people came to court as more of a witch hunt ... to burn him at the stake," Turko said.
Turko also asked jurors to consider wrongful convictions in making their decision.
"Most of these have been convicted on circumstantial evidence or evidence of an informant," she said. "I know how most of you would feel if you had a loved one wrongfully convicted."
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 mean 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," Firestone said.
"In order for you to convict Mr Beckett, the Crown does not have to prove how she was killed ... only that he was responsible."
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."
At many points during Firestone's closing argument, Beckett could be seen shaking his head emphatically in his seat in the courtroom.
Beckett and Letts-Beckett met in 1995 in New Zealand. Five years later, he moved to Westlock, Alberta, to be closer to 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.
Letts-Beckett also went to police alleging physical abuse on the part of her husband, but no charges were laid.
- Additional reporting: Hawkes Bay Today
