Jaina Jansen (nee Tobias) is the main antagonist from "Sacrifice", episode 3.07 of Law & Order: SVU.
Jaina Jansen was born Jaina Tobias in Arkansas, and she was a childhood sweetheart of Wesley Jansen, who she later married. The couple gave birth to a daughter, Mara, who was born with cystic fibrosis, and to pay their daughter's medical bills, both Jaina and Wesley did pornographic films.
Jaina was first shown at the police station after Wesley was shot by their boss, Cal Owen; who ordered the hit when Wesley attempted to get Jaina out of the business. When Benson and Stabler encountered Jaina during filming, they were appalled to see Mara in attendance, with Jaina claiming that she could not find a sitter. Later on, Jaina received a lucrative offer to become a porn actress in Vegas; with the offer worth $50,000. However, it would all go to Cal due to Jaina working for him, and with that, Jaina shot and killed Cal; doing so while his back was turned. Wesley covered up for his wife and wiped her prints off the gun while putting his own on the weapon; and even pled guilty to the charges.
Meanwhile, the evil Jaina was looking to escape to the West Coast, before being caught and confronted by Benson and Stabler, who were under the impression that she was heading back to Arkansas. Jaina gave little regard over Wesley covering for her, and regarding Mara, she stated that she would send any money she makes to pay for her care. Benson and Stabler informed Jaina of her husband's innocence, and stated that they could perform a gun residue test that could prove she shot Cal. Jaina's attempt to claim self-defense rebuffed when she was reminded that Cal's back was turned, and following this, she confessed to the murder; claiming that Cal abused her and that she would not see a dime of the contract, while also venting about having to do porn while also taking care of a sick child. Jaina was eventually arrested for Cal's murder, and she was convicted and sentenced to 15 years in prison (off-screen).