Prosecutor Sarah Firestone has told jurors Beckett stood to gain a significant amount of money in life insurance and accidental-death benefits, as well as Letts-Beckett's school teachers' pension.
In court last week, jurors heard a number of wiretapped phone calls made by Beckett both before and after his August 2011 arrest.
The first call played was between Beckett and Margaret Blatchford, Letts-Beckett's aunt.
In the May 2011 conversation, Beckett tells Blatchford he's willing to fight for his share of his wife's inheritance.
"I'm still their son-in-law, right?" Beckett asked Blatchford.
"So what was due to Laura is certainly due to me. I'll challenge that in court any time."
"You'll challenge that in court, Peter?" Blatchford replied.
"Of course," Beckett said. "And I believe they caused her death."
Through her questioning, defence lawyer Donna Turko has implied Letts-Beckett struggled with depression, potentially because of issues with her family.
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. The Becketts split up 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.
Beckett's trial, which began in mid-January, is expected to last three months.
- Kamloops This Week