Brendan Banfield is now on trial for the murder of his wife, Christine, and the prosecution's star witness is Banfield's lover, the family's former nanny.

Juliana Peres Magalhaes, who was also charged, has agreed to testify as part of a plea deal. In exchange for her testimony, she will plead to the lesser charge of manslaughter, then walk free for time served.

She will then be deported back to Brazil.

The murder plot unfolded as Christine Banfield planned a fun day for her 4-year-old daughter, with a trip to the National Zoo with her Brazilian au pair, Magalhaes. The adult and child leave for the day, but turn around when Peres Magalhaes realizes she forgot their bagged lunches.

Arriving at the house, the au pair sees a car she doesn't recognize, and a man she doesn't know entering the house.

Confused, she calls her employer, Brendan Banfield, who tells her to stay in the car, and that he will be right home. Banfield is at the house in minutes, and they enter the house together.

The au pair takes the 4-year-old girl to the basement while Brendan Banfield goes upstairs to the master suite.

Brendan Banfield finds his wife, Christine, nude, with a man he doesn't know, holding a knife to her throat. Banfield tells cops he tells the man to put the knife down, but he starts stabbing the 37-year-old mother.

Brendan Banfield carries a gun as an IRS Special Agent, and he draws his service revolver and shoots the man in the head. The intruder is wounded and down on the ground. Banfield calls for Peres Magalhaes and tells the au pair to get his personal gun, a Glock, out of the bathroom safe.

Giving her the code, the au pair retrieves the Glock and, at Banfield's direction, shoots Joseph Ryan through the heart as he is lying on the ground.

Investigators say, however, they believe the story told by Brendan Banfield and the nanny is a ruse.

Someone created the profile on the Adult Fetish website, pretending to be Christine Banfield, as part of an elaborate plan to kill Christine Banfield so her husband, Brendan, and their Brazilian live-in Au Pair could be together.

Investigators found pictures of Banfield and the au pair together in the Banfield bedroom, and Peres Magalhaes' clothes were found hanging in Banfield's closet.

Joining Nancy Grace today:

• Paul Batista - Prominent Criminal Defense Lawyer in NYC and Best-selling Novelist. Author of the textbook, "Civil RICO, Fourth Edition" 
• Dr. John Delatorre -  Licensed Psychologist and Mediator (specializing in forensic psychology); Psychological Consultant to Project Absentis: a nonprofit organization that searches for missing persons; X, IG, and TikTok - @drjohndelatorre
• Dr. Kendall Crowns - Chief Medical Examiner Tarrant County (Ft Worth), Host of Podcast, "Mayhem in the Morgue," and Lecturer: Burnett School of Medicine at TCU (Texas Christian University)
• Gigi McKelvey - Journalist, Host of the podcast “Pretty Lies and Alibis” prettyliesandalibis.org, Facebook, IG, TikTok: @PrettyLiesAndAlibis, Twitter: @PrettiesLiesAlibi 
• Sydney Sumner  - Investigative Reporter, ‘Crime Stories’ 

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