The sentencing hearing of Molly Martens and her father Thomas in the US will hear Victim Impact Statements from Jason Corbett's children in the coming days.
Mr Corbett (39) was beaten to death with a baseball bat and a concrete paving slab in his North Carolina home in 2015.
Ms Martens and her father were originally convicted of his murder; however, the North Carolina Supreme Court later ordered a retrial.
They have accepted charges of voluntary manslaughter as part of a plea deal, and a court in Lexington has been hearing submissions ahead of sentencing.
Freelance Journalist Brian Carroll told Newstalk Breakfast the court heard evidence from an expert witness in domestic violence, Dr Scott Hampton, on Tuesday.
"He was basically speaking in general terms about the kind of characteristics you see in a household where there is domestic violence," he said.
"He tried to graft that on to Jason Corbett's home, but the expert was really eviscerated in cross-examination by Alan Martin, the Assistant District Attorney.
"The expert had alleged that Molly was all about the kids, and that on the night of the killing the last thing she wanted was for Jason to die."
Crime scene photos
Mr Carroll said it was alleged by the expert that if Mr Corbett died, Ms Martens would have no rights over the children.
"He was arguing that she had no good reason to do what she did on the night, and the only driving factor for her was to keep the children so she had to keep Jason alive," he said.
"The District Attorney... really attacked this witness, to the point where he took out four of the crime scene photographs.
"He showed him a photograph of Tom Martens and Molly Martens, both of whom didn't have a mark on them.
"Then he showed him autopsy photographs of Jason Corbett... and he asked the expert witness, 'Were there good reasons for these injuries?'
"The witness responded that it just showed how terrified the Martens were on the night.
"This brought derisive laughter from the Corbett family in the public gallery, which has been the first show of emotion or outburst from anybody over the last eight days.
"The judge immediately warned them they would be removed from the court if there was any outward reaction to any testimony being given".
Mr Carroll said character witnesses were also called for Mr Martens.
"What we had yesterday was a series of expert opinions and character witnesses on behalf of Tom Martens," he said.
"These were people who had worked with Tom Martens in the FBI, and they included Tom Martens brother-in-law Mike Earnest who is also a federal agent.
"The Martens family are kind of steeped in law enforcement; Tom, of course, had 30 years in the FBI and then became a counter-intelligence officer.
"We were hearing, basically, character testimony from friends and colleagues of Tom Martens yesterday," he added.
Mr Carroll said closing arguments will be heard over the next two days, followed by Victim Impact Statements from Mr Corbett's two children.
"The very last voice that the judge hears before he hands down sentence will be those of Jack and Sarah, Jason's children," he added.
Molly and Thomas Martens could face a sentence ranging from 17 years to parole.