|Affiliation||Reichian Therapy League|
|Occupation|| Jailhouse lawyer|
|Pathology|| Drug dealer|
Convicted proxy murderer
|Family|| Carla Lowenstein (ex-wife)|
Dierdre Lowenstein (daughter; deceased)
Ezra Lowenstein (son)
Jacob built a psychiatric practice with Reichian Therapy League until he was fired for his cocaine use. He eventually set up his own practice and started dealing cocaine to his patients. He met a woman named Carla at an unknown point in his life and married her. At some point, Jacob became violent and began regularly beating Carla. They eventually had two children, Didi and Ezra. He used cocaine to psychologically coerce her into hitting and abusing their children. He eventually started sexually abusing Didi as well and made Carla train her.
One day, Jacob forces Carla to strike Didi and then sends her to school. Detective Logan and Sergeant Greevey catch Jacob in a session with one of his patients. Logan then notices a bottle of cocaine on the table and takes him in on that while telling him about his daughter's condition in the hospital. When the police return to the house, they ask if Jacob hit her and he tries to intimidate her but she nods her head. Jacob tries to assault her again but is arrested by Greevay before he can. When he is arraigned, he makes bail while Carla remains in prison. When Didi dies, he and Carla are both charged with her assault and murder.
After Didi's teacher testifies, Carla accepts a plea and later testifies against Jacob. During testimony, Jacob repeatedly interrupts and the judge reprimands him both times. Jacob testifies that he never hit Didi, that he loved her, and that Carla is insane. On cross-examination, EADA Stone gets him to admit he sells drugs illegally to his patients while he repeatedly denies the abuse. Stone points out the bloodstain on their carpet and Jacob tries to deny any knowledge of it. However, Stone convinces the jury that after his daughter was injured, he just left her. Jacob is found guilty of murder in the second degree and sentenced to 25 years to life in Sing Sing Correctional Facility. (L&O: "Indifference")
Jacob earns a law degree inside prison, allowing him to work with other prisoners on their appeals to protect himself inside. Jacob is later paroled after serving 15 years and starts living with a woman named Sheryl and her children. He is run over by his therapist, Joyce Draper, and is hospitalized. Jacob eventually wakes up and asks to talk to the detectives working on his case. When they arrive, he claims the hit-and-run was deliberate. During the questioning, he still refuses to accept responsibility and blames everyone else for his incarceration, treatment, and hit-and-run. He later dies from his injuries at the hospital and Joyce is not convicted of killing him. (L&O: "Fixed")
- Carla Lowenstein (his wife; emotionally abused and repeatedly beaten)
- Deirdre Lowenstein (his daughter; sexually molested and coerced Carla to beat and physically abuse her; eventually died from her injuries in the hospital)
- Ezra Lowenstein (his son; coerced Carla to beat and physically abuse him)
- Emily (assaulted; broke her arm)