Leslie Le Zard is a corrupt official in the Food and Drug Administration who lied on her resumé about going to Yale and running marathons. She allowed passes on dangerous medical products so she'd profit from kickbacks. This endangered and killed of many consumers and patients, including Jacqueline Borden's son Toby Borden and her daughter. She, however, blamed local dentist Norm Goldman for killing her son and thus murdered him in revenge.
In the effort to cover her actions and silence witnesses, Le Zard killed Jim Kettle by giving him a defective inhaler and a jacket covered in cat fur, which Jim was allergic too. She also set up her boss Marty Palin as the culprit. This didn't work and Goren and Eames arrested her as a result of her actions.
Before she was removed, Le Zard taunted Goren and Eames over how they wouldn't advance in their own careers, revealing she did research on them. (CI: "Smile")