Carissa is a woman with long, dark hair and brown eyes with pale skin. Considering she's a professor, this likely suggests she will be wearing corporate casual attire to possibly a lab coat depending on what she teaches.
While she was Professor Gellar's teaching assistant she worked with him on a Lamb ritual where she laid down naked with a dead lamb on her head. She would eventually develop a sexual relationship with the Professor until she discovered that he always did this with all his assistants. She broke up with him and eventaully earned her doctorate and became a professor herself.
She is first questioned by Detective Joey Quinn and Sergeant Angel Batista regarding Gellar's connection to the Doomsday killings. She firmly says that Gellar cannot be connected to these killings in any way and is willing to help them find him just to prove they have the wrong man. Quinn eventually decides to get involved with her and spend the night together. Batista comes over to pick Quinn up and Carissa opens the door and lets him in. Angel then finds a book of Gellar's and calls her into the room. At first she is furious at him for going through his stuff but changes her tone when she sees the similarities between his drawings and the killings.
After it is discovered that she is the one helping Gellar with his Lamb ritual in a local newspaper she is called in by Lieutenant Debra Morgan for more information. She is questioned by Sergeant Batista which she is very uncomfortable answering questions. It only get more uncomfortable as Morgan sends Detective Quinn into the interrogation as well not knowing of their affair. Carissa eventually blows up, stating that they are to stay away from her or she will sue the department over Quinn's actions and storms out of the building.