Tessa McKellen (Rebecca De Mornay) is the main villainess of "Manipulated", episode 7.15 of Law & Order: SVU (airdate February 7, 2006).
Tessa was the daughter of an attorney and grew up to follow in her father's footsteps, becoming a lawyer and working for his law firm (taking over the entire operation after his death). In 2003, she and her husband Linus McKellen were driving one night when their car hit a patch of black ice, causing Linus to crash, with the accident leaving Tessa temporarily paralyzed. But when her paralysis healed, the evil Tessa had grown to enjoy her husband doting on her and began pretending she was still paralyzed. She continued her work at the firm, though, alongside her associate Vicky Riggs.
When Tessa began having suspicions that Linus had been unfaithful, she hired private investigator and former Silverhammer employee Walter Inman (her having previously defended his company) to follow Linus and steal viruses for her to prolong her illness. Walter reported back to Tessa and told her that Linus had had flings with both Vicky and stripper Josie Post, though Josie had only provided her apartment to Vicky--who had been secretly working as a stripper as well--so she and Linus could continue their dalliance.
Furious and vengeful, Tessa hired Walter to kill Vicky and Josie, giving him Linus's semen to frame him for the murders. When Tessa was first questioned by detectives Benson and Stabler, she fingered the strip club that her firm handled a case against, intentionally leading them to uncover Vicky's double life. She also played the role of the caring and supportive wife when the detectives began suspecting Linus of being behind the murders, masking her true plan. Tessa's plan hit a snag, though, when Walter forgot to unlock the front door after killing Josie, proving to the detectives that he entered through the window.
When Inman was uncovered as Tessa's hitman for hire, Novak made a deal with him so he would confess that Tessa had hired him to kill Vicky and Josie, as well as steal viruses from a lab for her (this revealing that she was making herself sick). Benson and Stabler arrested Tessa just as she was preparing to inject herself with a needle, though it was later shown to contain insulin for her diabetes. Tessa's attorney decides to use a psychiatric defense, saying that Tessa's Munchausen made her incompetent to assist in her defense. But despite Dr. George Huang arguing that Tessa's disability had no effect on her decision making, the evil Tessa managed to convince Judge Lena Petrovsky otherwise by overdosing on insulin during her competency hearing, causing her to have a seizure. But Benson and Stabler were able to corner Tessa by revealing her true nature to Linus, who came to realize the truth when he realized that Tessa had manipulated him into never taking her to her doctor so that he wouldn't discover her secret. Angered, Linus fully exposed Tessa by shoving her into their pool, forcing her to realize that she was no longer paralyzed. Linus stormed away in disgust and Tessa was arrested offscreen.
- Tessa McKellen is similar to Sarah Sinclair from McBride: Dogged: both are women who are injured in car accidents and falsify the severity of their injuries to their husbands, while also orchestrating vengeful schemes to punish their husbands for having an affair. Though while Tessa's falsfication of her injuries were out of a desire to be cared for, Sarah's was purely done as part of her revenge plot. Additionally, Tessa killed her husband's mistress and framed him for the crime, while Sarah killed her husband and framed his mistress.
- Rebecca De Mornay is also known for playing the psychotic Mrs. Mott from 1992's The Hand That Rocks The Cradle and sociopath Natalie Koffin from the 2010 remake of Mother's Day.