Editor's Note: A warning that this story contains details that some people may find disturbing. Discretion is advised.
The bedroom of a Herndon family's home was stained in blood.
Christine Banfield, a 37-year-old married mother of a 4-year-old girl, lay stabbed several times. Nearby, a stranger was dead.
Banfield's husband, Brendan, and the family's au pair, Juliana Peres Magalhaes, had entered the second floor suite a few moments earlier. The two claimed the stranger attacked Christine leaving her seriously wounded.
Brendan grabbed a gun and shot the alleged intruder. The initial shooting didn't kill him so Brendan Banfield told his daughter's caregiver to get another gun so they could shoot him again. She did.
The shocking scene was described to detectives as an act of defense. Prosecutors, however, claim evidence points to a very different story.
Fairfax County authorities on Monday outlined a mysterious series of events leading up to the double homicide as part of a hearing to decide whether Peres Magalhaes should stand trial for 39-year-old Joseph Ryan's murder.
A double killing
U.S. & World
Get a weekly recap of the latest San Francisco Bay Area housing news. >Sign up for NBC Bay Area’s Housing Deconstructed newsletter.
It was around 7:30 a.m. on Feb. 24, 2023, when Peres Magalhaes left the Banfields' Stable Brook Way home with their daughter, according to detectives. The 23-year-old told police she doubled back to the home because she forgot to grab packed lunches. When she arrived, Peres Magalhaes, a Brazilian-national who also lived in the home, saw a car she didn't recognize.
She called Christine, but when the mother didn't answer, Peres Magalhaes phoned Brendan, who quickly came home, authorities said.
Minutes later, the pair and the child entered the home. Brendan then went upstairs to the bedroom where he found Christine and Ryan.
Detectives say the two claimed Ryan had attacked Christine, prompting Brendan — a law enforcement officer for the Internal Revenue Service — to fire his weapon at Ryan.
Ryan had no obvious connection to the family or home other than the incident that cold winter day. But as detectives began probing how he supposedly found Christine, their case and the witness statements started to diverge.
A fetish site used as a lure?
A search of a computer in the Bandfields' home led detectives to a fetish sex website, prosecutors said. The site catered to sexual fantasies involving kinks, BDSM, and more.
Detectives found a profile for Christine and communications between her profile and Ryan. But authorities said something didn't add up.
They said the way Christine talked to Ryan in their messages was very different than how friends and family described her.
Police believe someone else was communicating with Ryan while pretending to be Christine — setting a meetup at the family's home for that day.
Nearly eight months after the killings, Fairfax County authorities arrested Peres Magalhaes and charged her with second-degree murder in Ryan's death.
"I suspected from the very beginning — and I went to the scene of that double murder — that there was going to be a lot of twist and turns to this investigation. The twists and turns are still on going," Fairfax County Police Chief Kevin Davis said as the investigation progressed.
"It's my expectation that we will eventually be able to hold more than just one person accountable for this crime."
A yet unproven theory
At Monday's hearing, prosecutors said they believe Brendan Banfield and Peres Magalhaes were having an affair. They stopped short of saying they believe the pair hatched a plan to get Christine out of the picture.
But they grilled Brendan about the events leading up to his wife's death. No one is charged in Christine's death.
Prosecutors presented evidence Monday they argue shows Brendan and the au pair went to a shooting range together a couple of months before the murders. Then the month before the killings, Brendan returned and bought a gun, authorities said.
The au pair told detectives Brendan shot Ryan first but he was still alive. She explained that Brendan told her to get the gun that he purchased from the shooting range to shoot Ryan again, according to detectives. She told police she did.
They also said both the au pair and husband swapped out their phones for new ones in the days leading up to the attack.
Prior to Peres Magalhaes' October 2023 arrest, detectives returned to the home.
Inside the bedroom Brendan shared with his wife and where Christine and Ryan were killed, picture frames are filled with photos of Brendan and the au pair.
Prosecutors say the au pair’s lingerie was found around the room. They described her as Banfield’s "girlfriend" and "live-in lover."
The prosecution’s theory is that the killings were part of an elaborate plan so Brendan and Magalhaes could live their lives without Christine. While the au pair denies she and Brendan were having an affair, prosecutors argue the new pictures on the nightstand suggest otherwise.
On the witness stand Monday, the widower largely invoked his Fifth Amendment right to decline answering pointed questions from prosecutors about the events leading up to the killings.
Fairfax County General Court Judge Michael J. Lindner called him an “adverse witness” but also said it appeared prosecutors “may be playing two prospective defendants against each other.”
In a foreshadowing of defense arguments that could be laid out at trial, Peres Magalhaes’ attorney Ryan Campbell attempted to cast doubt on who fired the shot that killed Ryan. And he decried prosecutors’ decision to call Brendan Banfield to the stand, saying: “It’s been clear from the beginning [Banfield is] the target of the investigation.”
Brendan Banfield is not charged with a crime. He had no comment when asked by News4 outside Fairfax County court Monday.
Judge Lindner allowed the case against Peres Magalhaes progress. Her attorneys have previously argued that she shot Ryan in self-defense. Requests for additional comment made Monday were not immediately returned.
A grand jury will be convened in the case later in April.
