A woman has come forward with creepy details about an affair she had with Brendan Banfield years before he murdered his wife in a bizarre, fetish fantasy plot so that he could run off with his au pair.
The former lover broke her silence in an upcoming episode of ABC’s 20/20, out Friday, after Banfield was convicted of the murders of his wife Christine Banfield, 37, and a stranger Joseph Ryan, 39, earlier this month.
In an exclusive clip of the show obtained by the Daily Mail, the woman - under the pseudonym Jennifer - revealed that Banfield carried out what he described as ‘CSI sweeps’ after bringing her in to the home he shared with Christine.
‘He would do these very detailed cleanings after I leave because I have different colored hair from his wife,’ Jennifer told 20/20 co-anchor Deborah Roberts. ‘He called it a CSI sweep.'
To him, she noticed it was 'like a game' and that it gave him a 'thrill.'
'I think he almost liked it. It was almost like a game. There is a thrill to doing forbidden things.'
Jennifer said she went to the couple’s home for their illicit hook-ups ‘all the time.'
‘He was very nonchalant about having me in his home. It didn't bother him at all,’ she said.
Brendan Banfield murdered his wife Christine so he could run off with their Brazilian au pair Juliana Peres Magalhaes (Banfield and Magalhaes together)
The Banfields with their young daughter. Banfield, a former IRS agent, posed as his wife on BDSM site Fetlife
At the time, Christine - an ICU nurse - had a job that meant she was away from home a lot of the time, so she and Banfield would spend long days and weekends together at the marital home.
Years after their illicit rendezvous ended, the the IRS agent's latest extramarital affair took a twisted, deadly turn.
On February 24, 2023, Christine and Ryan were murdered inside the Banfields’ $1 million home in the affluent, safe neighborhood of Herndon, Virginia.
Banfield, 40, and the couple’s Brazilian au pair, Juliana Peres Magalhaes, 25, told police they had returned home to find Ryan stabbing Christine to death.
They claimed they both pulled out guns and shot Ryan dead.
Within months, Banfield moved the au pair into the couple’s bedroom and replaced photos of his wife in the room with pictures of them.
Jennifer remembers the moment she learned of Christine’s death - and the gut-wrenching realization that Banfield could be her killer.
Years had passed since her own affair with Banfield and she just happened to check up on him.
‘It was one of those Googling things where I was checking up on him again,’ she told 20/20.
Banfield's former lover is breaking her silence in an upcoming episode of ABC’s 20/20, out Friday
The Banfields' $1 million home where Christine Banfield and Joseph Ryan were murdered
‘It was in news articles and I’m like ‘why would he be in the news?’
‘Then when I saw the name of the person who was killed, [I thought] ‘is that not his wife?’’
She added: ‘And so the first thought in my head was: ‘oh my god, he killed her.’’
It didn’t take long for investigators to come to the same conclusion.
Very quickly, Banfield and Magalhaes’s story started to unravel - and their warped secrets came to light.
Banfield and Magalhaes had masterminded a complex, bizarre plot to ‘get rid’ of Christine because they were having an affair.
The two lovers had been posing as Christine on BDSM and fetish fantasy website Fetlife, seeking out a patsy that they could lure in and then frame for Christine’s murder.
Ultimately, they selected Ryan for the job.
Posing as Christine, they gave Ryan detailed instructions for the sexual fantasy: to enter the home while she was asleep in bed, go upstairs, cut off her clothing, tie her up and rape her.
Then, they would enter the home and shoot Ryan dead.
Banfield would then stab Christine to death, claiming Ryan was her killer.
Banfield and Magalhaes were both arrested and charged with murder in October 2023.
When she heard of the arrests, Jennifer told 20/20 she contacted investigators to tell them about their own past affair. She said she wanted them to know what Banfield's character was like.
Behind bars, both Banfield and Magalhaes maintained their innocence for a year.
Then, in October 2024, Magalhaes flipped, agreeing to cooperate with prosecutors and testify against Banfield in exchange for a plea deal where she pleaded guilty to a lesser charge of involuntary manslaughter.
When Banfield went on trial in Fairfax County Circuit Court in January, she was the star witness.
Brendan Banfield was convicted of all charges earlier this month and is facing life in prison
Banfield moved his au pair-turned-lover into the marital bed just months after Christine's murder
Photos of the Banfields had also been replaced by a framed picture of Magalhaes and Banfield next to the bed
Over three days of testimony, she told jurors how she and Banfield began having an affair the summer after she moved in to the couple’s home to care for their daughter.
It was not long before Banfield began talking about killing Christine and moving to Brazil with her to start a new life, she testified. Magalhaes claimed divorce was not an option for Banfield because he did not want to lose money or custody of his daughter.
She and Banfield used Christine’s laptop to create a fake email address and Fetlife account and were careful to use the account when Christine was also in the home, she said.
Banfield also bought a gun just before the murders and had special triple-glazed, noise-reducing windows installed in the home to muffle the sounds of gunshots and screams.
Jurors were also shown 'red, lingerie-style clothing items' and Magalhaes’s other belongings hanging in the primary closet after the au pair moved into the bedroom just after the murders.
Banfield also took the stand at his rial, admitting that he had cheated on his wife with several women but proclaiming his innocence of her murder.
He branded the sexual fantasy murder plot as ‘absurd’ and ‘absolutely crazy.’
The jury didn’t agree.
Christine Banfield, 37, and Joseph Ryan, 39, were killed at the Banfields' home in Herndon, Virginia
Banfield was convicted of two counts of aggravated murder, one count of use of a firearm in the commission of a felony earlier this month.
He was also convicted of child abuse and felony child cruelty, in connection with the Banfields' then-four-year-old daughter being inside the home at the time of the murders.
He is facing life in prison at his sentencing, scheduled for May 8.
Under the terms of Magalhaes’s plea agreement, prosecutors had recommended she be sentenced to only time served. But a judge sentenced her to 10 years in prison and two years suspended days after Banfield’s conviction.
