Lisa Randall is an incidental character who appeared in The Itch.
Lisa had a daughter named Olivia, but she died when she was three years old due to being born prematurely. Afterwards, her husband left her. Lisa later mentions that before her death, Olivia's skin seemed to be undergoing an unspecified condition (she never finished her sentence regarding it). Afterwards, she began suffering an itching disorder and relied on baby rash cream for remedying it. Lisa also suffered from arachnophobia. Her suffering caused her to develop anti-government views. Motivated to help others, she started a support group for sufferers of Morgellons syndrome, a condition that caused one afflicted with it to believe he or she was infested with insects or fibers. Two of the group's members were Jane Posner, whom she befriended, and Leo Jenkins, whom she became wary of due to his unsettling and extremely paranoid nature.
Lisa is first seen having a meeting with her support group, where Jane explains the story about her sickness. Afterwards, Lisa tells everyone to stand up, join hands, and end their meeting with their prayers. Later, Morgan and JJ interrogate Lisa, who believes the FBI looks down upon her and others with similar conditions, and wants them scared and isolated. Morgan says that they have no opinion about her condition and show her pictures of murder victims. They tell her that a member of her support group has a sickness about insects inside him and asks if she knows anyone has it, but she doesn't give anyone away. They also warn Lisa that she could be the killer's next target. The next morning, Lisa comes to Jane's apartment and wakes her up. Then, Lisa receives a call from JJ and replies to her that she will come down to the police station.
Hotch interrogates her, and asks her about her sickness and Olivia. He then expresses his knowledge that Lisa wants to help the people who come to her meetings and that she wants to help the BAU. She finally tells Hotch about Leo and adds that she heard someone in Jane's apartment talking to her. A police officer later takes Lisa back to her house, unaware that Leo is in his car watching her. When Lisa goes to her car, Leo ambushes her and demands to know what she told the BAU; though she replies she didn't tell them anything, Leo doesn't believe her and knocks her out. Later, Lisa regains consciousness, tied up in the basement of Leo's house. When Lisa positively answers Leo's question about being afraid of spiders, Leo puts several spiders on Lisa as a form of torture, but she keeps denying about working with anyone. Then, the BAU show up, subdue Leo, and rescue Lisa. At the end of the episode, Lisa is last seen at home. She looks at a picture of Olivia and smiles.