Ex-IRS special agent Brendan Banfield Friday was found guilty of murdering his wife and a sex-seeking stranger whom prosecutors alleged he lured to the couple’s suburban Washington, DC, mansion as part of an elaborate plot he hatched with his Brazilian nanny-turned-mistress.

The 40-year-old former fed was convictedby a jury in Fairfax, Virginia, of killing wife Christine, 37, and Joseph Ryan, 38. Prosecutors say Ryan arrived at Banfield’s Herndon home believing he was meeting Christine for a kinky rendezvous on Feb. 24, 2023.

Brandan Banfield was also convicted of using a weapon for the murders and of endangering his then-4-year-old daughter by leaving her unattended in the basement while the carnage unfolded.

The panel consisting of seven women and five men reached the verdict after nine hours of deliberation.

Banfield appeared disappointed, bowing his head slightly and casting his eyes downward as the verdict was read out.

He faces life in prison without the possibility of parole at his sentencing on May 8.

Fairfax Commonwealth’s Attorney Steve Descano told reporters at a press conference after that Banfield’s choice to make up the twisted story and then double down on it when he testified before the jury was “monstrous.”

“We don’t have a lot of homicides,” Descano said of Fairfax County. “I have been doing this job a while and I can tell you that this defendant stood out to me highest above all the other murder cases that we have done in my six years here.” 

The prosecutor said “it was a very very emotional day” for the victims’ families. 

“I hope this verdict gives them some sense of peace and puts them somewhere on the path towards healing after this tragic, tragic homicide,” Descano said.

Over the course of the sordid three-week trial, the 12-person jury heard from both Banfield’s Brazilian au pair, Juliana Peres Magalhães, 25, and from Banfield himself — when he took the rare step of testifying in his own defense.

Magalhães — who pleaded guilty as part of a prosecution agreement for a sentence of time served — testified that mere months after she began sleeping with her married employer, the duo started cooking up a twisted scheme to kill Christine.

The pair started a fetish account, pretending to be the mom-of-one, and lured in Ryan to supposedly help Christine live out her supposed fantasy of being raped, the nanny testified.

Ryan came to the Banfield’s home, armed with a knife as instructed, and began playing out the kinky sex-session with an unwitting, Christine — who was previously a nurse for sexual assault victims — the au pair claimed.

Magalhães, who looked after the Banfield’s daughter, waited in a car outside the house, calling Banfield and telling him an intruder was in their house — but it was all part of an elaborate frame-job, according to prosecutors.

Banfield rushed home, and went inside with Magalhães, leaving the young girl alone in the basement while the gruesome scene unfolded upstairs.

The philandering husband shot Ryan with his service weapon to make it look like he’d bravely saved his wife from an attack, and then stabbed Christine multiple times in the neck, trying to doctor the scene to appear as though Ryan killed her, the nanny said.

Banfield admitted to the romance with the au pair, admitted he’d cheated before and said Christine had also slept with other men and was into BDSM.

The accused murderer also copped to jurors that he shot Ryan, maintaining it was in defense of his wife and not part of a cold-blooded plan.

During closing arguments Friday morning, Banfield’s lawyer, John Carroll, told the panelists Magalhães made up the whole story to save her own skin and get off scot free.

“Juliana made it up,” Carroll said. “She told the commonwealth what they wanted to hear.”

“Her entire story has been bought and paid for,” said Carroll, adding that not only would she skirt hard time but also had the opportunity to sell her story to be made into a documentary.

But prosecutor Jenna Sands told the jury there was a mountain of incriminating evidence against Banfield — including but not limited to the former nanny’s damning testimony.

“He was in love with Juliana,” Sands said. “He can pretend this was a fling … He was afraid of losing her. He needed to get rid of his wife so they could be together, so they could get married, so they could have children together.”

Banfield has maintained his innocence.

Magalhães is expected to be sentenced in the near future now that Banfield’s trial has wrapped.