Reginald Mathis is a drug dealer and the attempted murderer of teen informant Kevin Stanton, consequentially leading to Mathis killing Kevin’s friend, Sara Teasdale. Kevin was sent by narcotics detective Mark Rivera to catch Mathis in a sting that went awry, Rivera deliberately withholding emergency response to cover his own tracks.
Mathis’ conviction depended on the testimonies of Kevin, Mathis’ accomplice Oscar Benvenidez, and Rivera, who was the trickiest to crack because he was pressured with a manslaughter charge. In the end, Mathis was imprisoned for murder (L&O: "Bait")