A Brazilian au pair who fell in love with an IRS agent pleaded guilty to manslaughter on Tuesday in what prosecutors say was an elaborate double-murder scheme to frame another man in the stabbing of his wife.

For months after the killings on Feb. 24, 2023, it might have seemed as if Juliana Peres Magalhães and the IRS agent, Brendan Banfield, got away with murders, according to new details prosecutors revealed in court to support her guilty plea.

Christine Banfield, a pediatric intensive care nurse with a 4-year-old daughter, had been mortally wounded with stab wounds to her neck, and Brendan Banfield, her husband, and their live-in nanny both said they shot her apparent killer — a man who had been lured to the bedroom with promises of rough sex.

Magalhães had called 911 to the house in Herndon, Virginia, and was hyperventilating at the scene as she described the killings. Detectives weren’t buying it — but it took time to build their case. Meanwhile, the live-in au pair moved into the primary bedroom with Banfield and posted photos of them as a couple, authorities said. When she was arrested in October 2023, a picture of herself with Brendan Banfield was on the nightstand.

As she remained in jail for more than a year thereafter, she declined to say anything more.

A long-awaited forensics report on the blood spatter evidence then came in, and prosecutors said it showed that Brendan Banfield had smeared blood from Christine Banfield’s wounds onto the body of Joe Ryan, the man they had tried to frame for stabbing her. Authorities arrested Brendan Banfield in September on charges of aggravated murder.

Banfield’s lawyer, John F. Carroll, said in court before he was denied bail in September that the evidence “just doesn’t add up” to him killing his wife.

In October, Magalhães agreed to cooperate with the police in her second interview since the day of the crime. Days later, on Tuesday, two weeks before she was scheduled to go to trial on charges of second-degree murder and felony firearm use, Magalhães pleaded guilty to Ryan’s killing, saying she had agreed to help the husband’s ruse to kill the wife and make it look like they both shot a predator.

“Are you entering your guilty plea because you are in fact guilty of this offense?” Chief Judge Penney Azcarate asked Magalhães before accepting her plea to a single count of manslaughter, reduced from murder and a firearm offense.

“Yes,” she replied, softly.

The sentencing of Magalhães, who was raised in the outskirts of Sao Paulo, now awaits the conclusion of Brendan Banfield’s trial. Depending on her cooperation with authorities, attorneys said in court that they may agree for her to be sentenced to the time she’s already served.

“Much of the information that led to this agreement cannot be made public at this time, due to the upcoming criminal trial against the other defendant in this matter,” Fairfax County Commonwealth’s Attorney Steve Descano said.