Accused wife-killer Brendan Banfield told his au pair and alleged accomplice he was “obsessed” with her happiness in love letters, and discussed baby names for their future child in text messages, a Virginia jury heard before testimony wrapped in the lurid murder trial.

The former federal agent, 40, was grilled on the stand during his cross-examination Thursday over the alleged murder of his wife, Christine, and a stranger, Joseph Ryan, as part of a twisted and elaborate rape and killing plot to be with his Brazilian au pair-turned-mistress. 

“I am obsessed with your happiness,” the prosecutor read from a 14-page love letter Banfield reportedly wrote to his child’s nanny, Juliana Peres Magalhães, with whom he admitted to having an affair.

Banfield told Magalhães in the letter written from jail that he had “never had a consistent partner before,” the prosecutor read.

The jury was also shown messages of Banfield and Magalhães discussing baby names for their future children on the encrypted messaging app Discord.

“That is something that she wanted to talk about,” Banfield told the prosecutor, referring to Magalhães.

Banfield, who denies the Feb. 24, 2023, double murder, told the prosecutor that Magalhães was his “hero,” because she had “saved my life” on the day of the killings.

“I think it’s easier to fall in love with somebody that saved you,” he said. 

In his testimony, Banfield said that his affair with Magalhães began after she complained to him one night about dating apps while Christine wasn’t home.

During redirect, Banfield claimed that the pair had had multiple affairs over the years, and said Christine had a “BDSM affair” with someone when they lived in New York before moving to Virginia.

He said he learned about the affair after spotting bruises on his wife’s arm.

Banfield claimed that Christine, who worked as a sexual assault nurse examiner at the time, was interested in sexual violence.

“She did many examinations of both men and women … people that were raped, some pretty graphic things. She used to bring, she used to bring some of her documents home. So I was aware that she, she seemed to look at them relatively often,” Banfield said.

In his testimony on Wednesday, Banfield said the accusation that he had plotted his wife’s murder was “absolutely crazy.”

To make matters more bizarre, prosecutor Jenna Sands told the judge after Thursday’s lunch break that a man had asked a Fairfax County detective if it was too late for him to testify — and that two jurors were nearby at the time and could have heard the question.

Sands said the detective immediately halted the conversation, pulling the man away from the two panelists. The issue was discussed further in secret by the judge’s bench before trial resumed.

Testimony concluded Thursday afternoon after three-weeks of witnesses taking the stand. 

Lawyers on both sides are set to deliver closing arguments Friday morning before the jurors are sent to start deliberating.