As a child, Lewis had to travel around the world because of her father Albert's service in the U.S. Army. She also had a mother who died of breast cancer and a brother named Gabriel. As a child, she and her family moved to Germany. There, she was harassed by a bully named Martin Gumbel, who made fun of her name and drew a swastika on her locker. When Gabriel reported it to the school administration, Gumbel and his friends sought revenge by beating him up. As a result of the incident, Lewis admired her brother for always standing up for her, while he started calling her "T". As an adult, she had high intelligence alongside Gabriel, though Gabriel forsake it in favor of getting rich, while she went to Dartmouth College. Lewis eventually had to help Gabriel through the aftermath of one of his scams and tried to get him to change his ways, but her efforts were unsuccessful, leading to an estrangement between the two. She joined the FBI as a forensic psychologist, who extensively interviews a number of psychopathic criminals to determine whether they were fit for trial or not. Through her job, she has seen a number of depraved minds up close and personal. Before joining the BAU, she came from the San Francisco FBI field office. More recently, she is engaged to a man named Doug Fuller, which caused her some personal distress after other women began flirting with him.
To be added
In "Mirror Image", Gabriel is abducted by Peter Lewis, who brainwashes a man named Desmond Holt to take Gabriel's place. Upon realizing this, Lewis is able to profile where Gabriel is located and saves him, narrowly escaping Peter's trap in the process.
In the season finale "Red Light", the team gets a new lead on Peter's current location. However, their SUVs were disabled by spike-strips and struck by a semi-truck. The SUV Lewis was in took most of the impact, and it is currently unknown if she survived the attack.
- She interviewed Loren Herzog, one of the Speed Freak Killers. (The Job)
- She interviewed Archie Sutton, a.k.a. "The Truck Stop Strangler", an infamous serial killer whose mother was coincidentally the elementary school classmate of Lewis's own mother. (The Witness)
- Her father owned an auto repair shop and taught her how to repair old cars. (Drive)
- She is the same blood type as Savannah Hayes. (A Beautiful Disaster)
- She speaks German (Devil's Backbone) and French. (The Storm)