The defense for Brendan Banfield spent Thursday challenging how, when and why Fairfax County, Virginia, police and prosecutors reached the decision to charge the Herndon man with aggravated murder in the February 2023 deaths of his wife Christine and another man, Joseph Ryan.
Prosecutors say Banfield killed them both as part of an elaborate plot with the family’s au pair, Juliana Peres Magalhães, to kill his wife and blame it on Ryan.
In the second day of the defense’s case, attorney John Carroll focused on his opening‑statement claim that Fairfax County police struggled to find evidence to match prosecutors’ “catfishing theory.” As part of that theory, prosecutors say Banfield and Magalhães created a profile impersonating his wife on a fetish website to lure a man to the family home, so he could kill his wife and claim he’d interrupted a home invasion.
Magalhães, who was having an affair with the husband, was initially charged with murder, but pleaded guilty to a reduced charge of manslaughter in 2024.
Police detective Matthew Nilssen, called as a defense witness, testified that Magalhães was arrested and charged with murder long before she eventually told prosecutors of her involvement.
“Based on our investigation, there was a belief that there was more to the story that could be elicited from her,” Nilssen said. “There is competing interests between self-interest and cooperation, and by introducing circumstances that would encourage cooperation with law enforcement over cooperation with other parties, it could change the outcome of the investigation … and amount of information available to us, as investigators.”
Homicide detective Leah Smith said one week after Christine and Ryan were killed, investigators were given a briefing.
“Our supervisor at the time told us there were two theories in the case, and we needed to get behind the right one,” she said.
Smith said supervisors didn’t provide specifics of the “catfishing theory,” but she told the supervisor and a room full of investigators, “At this point in time, nobody should have a theory in this case, that we were still at the very beginning and we should only be investigating and gathering facts and information.”
Carroll asked Smith how her superiors reacted to her statement.
“There was no response,” she said.
Several witnesses were asked about how and why Brendan Miller, who was the initial lead investigator, was transferred off the case.
Deputy Chief of Major Crimes Patrick Brusch, who was a captain in 2024, said it was his decision to remove Miller from the case, after Miller provided an executive summary that concluded that Christine never lost control over her phone and laptop. That conclusion ran counter to prosecutors’ theory that Brendan Banfield and Magalhães used Christine’s devices to communicate with Ryan and other men as they were staging the scenario.
Shown his texts and emails, Brusch said, “I had indicated that as far as I was concerned, Detective Miller was not to work another digital forensic case that pertained to the Major Crimes Bureau.”
Despite feeling pressure from her superiors, Smith said she didn’t change her tack: “No matter what they thought, or the theories they wanted to put forward, that was not how I was going to investigate or provide mentorship or counsel to other investigators on the squad.”
During cross-examination, prosecutor Jenna Sands asked Smith, “What was the turning point in your recollection of when Mr. Banfield was charged?”
“When we got the blood evidence back,” Smith answered.
Lt. David Giaccio specified that the blood in question was Christine’s, which was discovered on the socks of Magalhães and Brendan Banfield’s jeans.
He said information provided to detectives by the au pair was in line with the forensic evidence they had gathered.
“I think she filled in the blanks,” Giaccio said.
The trial, overseen by Fairfax County Circuit Court Chief Judge Penney Azcarate, is moving quickly.
Azcarate told jurors she expected they would continue the case next week.
On Thursday, jurors told Azcarate they would be willing to hear testimony Friday, in an attempt to complete testimony before this weekend’s expected winter weather.
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