Au pair who had an affair with Brendan Banfield testifying in his trial for the killings of his wife and another man

(CNN) — Brendan Banfield wanted to “get rid” of his wife so he killed her and another man in February 2023 in an elaborate scheme hatched with his family’s au pair – who was also his lover, a prosecutor told jurors Tuesday as Banfield’s double-murder trial got underway.

The family au pair, Juliana Peres Magalhães, is now on the witness stand testifying against Banfield.

Peres Magalhães was initially charged with murder in October 2023 and has since pleaded guilty to a lesser count of involuntary manslaughter for fatally shooting Joseph Ryan, one of the victims.

The au pair agreed to cooperate with prosecutors against Banfield in exchange for a recommendation that she be sentenced to time served, according to the plea agreement.

Banfield has pleaded not guilty to charges of aggravated murder for the deaths of his wife, Christine Banfield, and Ryan, as well as using a firearm during the commission of a felony. He faces up to life in prison if convicted on the murder charges.

Prosecutors say Brendan Banfield and the Virginia family’s Brazilian au pair were having an extra-marital affair and carried out the plan together. The salacious plot features allegations of BDSM sexual role play, trips to the gun range and false 911 calls, all in an attempt to kill Banfield’s wife and frame Ryan, according to prosecutors.

Banfield’s defense attorney countered that law enforcement manipulated evidence to pin the blame on his client.

In her opening statement Tuesday morning, prosecutor Jenna Sands told the jury Ryan had been lured to the Banfields’ home for what he thought was a consensual sexual encounter with Christine Banfield.

Brendan Banfield spent a month posing as his wife on a fetish website, cultivating a relationship with Ryan, who thought he was talking to Christine Banfield about her “stranger rape fantasy,” Sands told the jury.

“Those two individuals had no reason to know each other but for the plotting and planning of Brendan Banfield,” Sands said.

In his opening statement, defense attorney John Carroll said Peres Magalhães was arrested in October 2023 to pit her against Banfield.

“The whole reason she was arrested was to flip her against my client,” Carroll said.

Jurors hear 911 calls

The case began February 24, 2023. Calls to 911 led police to the Banfields’ Herndon, Virginia, home, where they found Christine Banfield, 37, dead of stab wounds, and Ryan, 39, dead of gunshot wounds nearby.

Tuesday morning jurors heard the 911 calls made from the Banfields’ home.

One 911 recording made at 7:47 a.m. was disconnected after a dispatcher answered the call. A dispatcher then called the number back and left a message when no one picked up.

Prosecutors have said Peres Magalhães called 911 at that point, but at Banfield’s direction, hung up before saying anything.

At 8:02 a.m. Peres Magalhães called 911 again and spoke to a dispatcher, stuttering but eventually telling them “her friend” had been stabbed.

“I need help …. my friend, she’s been stabbed with a knife and now she’s bleeding a lot. I don’t know what to do anymore,” Peres Magalhães could be heard saying.

After attempting to relay the home address to the dispatcher but stuttering and gasping for breath, Banfield took the phone from Peres Magalhães.

He gave his name and identified himself as a federal agent.
Banfield then said, stuttering at times on the recording, “There’s somebody here, I shot him. But he stabbed her. She’s bleeding. She’s got several marks on her neck. What do I do?”

Peres Magalhães pleaded guilty to involuntary manslaughter in October 2024, court records show. At a plea hearing, prosecutors read aloud a statement laying out the key allegations in the case.

As they alleged, Peres Magalhães began working as an au pair for the couple in late 2021, and in August 2022 she and Brendan Banfield began an extra-marital relationship. Banfield told his then-22-year-old lover his wife was a terrible mother and he wanted to “get rid” of her, Sands said in court. The murder plot was set in motion because, for Banfield, divorce wasn’t an option – he didn’t want to share custody of the couple’s toddler, the prosecutor said.

Banfield set up an account on Fetlife.com, a sexual fetish site, began communicating with Ryan and lured him to the Banfield home, prosecutors say. Ryan “likely believed” he was meeting Christine Banfield for a consensual sexual encounter, according to prosecutors.

Banfield, posing as his wife, gave Ryan strict instructions.

“The door will be unlocked. Christine will be asleep in bed. Come straight upstairs. Cut off the clothing. Tie her. Rape her. Simple and fun. That was how it was posed,” Sands said in court. “They would not meet in person beforehand. Joe’s phones would be left in a car. Joe was to bring a knife, zip ties, chains and, most importantly, he was not to stop even if she looked terrible, even if she was calling for help. He was to follow through, because that’s what she really wanted.”

Defense refutes ‘catfish’ theory

During opening statements, Banfield’s defense attorney accused law enforcement of manipulating evidence to fit the theory that Banfield “catfished” Ryan posing as his wife.

Initial digital forensics analysis conducted by investigators, however, found that Christine Banfield had control over her devices before her death, Carroll said Tuesday morning, and detectives who didn’t support the catfishing theory were removed from the case.

“In the world of digital forensics, there’s a saying, digital forensics doesn’t lie, people lie. And there’s going to be plenty to see. You’re going to see manipulation within the police department,” Carroll said.

Brendan Banfield and Peres Magalhães put his daughter in the basement and then went upstairs to the Banfields’ bedroom, with Brendan Banfield holding his service weapon and the au pair holding a firearm he had purchased a month earlier, according to prosecutors.

Banfield is a former IRS agent, according to CNN affiliate WUSA.

Banfield shot Ryan then stabbed his wife, according to prosecutors. Peres Magalhães then shot Ryan a second time at Banfield’s direction, Sands told the jury

Banfield spent the next several minutes manipulating the crime scene to make it appear like Ryan was an intruder, Sands said. The au pair then called 911 again and they reported the killings as if Ryan was an intruder who had stabbed Banfield’s wife, according to prosecutors.

In the commonwealth’s opening statement, Sands told jurors they won’t have to rely on testimony from Peres Magalhães because convincing “blood evidence” will be enough to convict Banfield.

“While Juliana presents us with the narrative, that story that we wouldn’t necessarily know but for her details, it is the blood evidence that you can rely upon without a doubt,” Sands said.

“The blood cannot lie, and the blood puts Brendan Banfield, standing over Christine, stabbing her in the neck until she died.”

As part of their plan, when Ryan came to the home, Peres Magalhães called Banfield to report that a strange man was at the house, and Banfield was waiting at a nearby McDonald’s so he could return to the home quickly, prosecutors have said.

Banfield was also indicted on a count of felony child abuse and neglect and felony child cruelty related to the killings in December 2024. His daughter, who was 4 at the time, was present at the scene, according to prosecutors.

This story has been updated with additional information.

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CNN’s Eric Levenson contributed to this report.