Alfonso Cardenas is one of two burglars and robbers of an elderly woman named Lenore Bernstein, following the lead of repeat offender Carlos Medina. Cardenas was submissive and usually answered to Medina's commands without thinking for himself, which is what happened when Lenore's apartment was burglarized and Lenore was tied up with her own stockings to her bed. When she didn't have much to steal, Medina ransacked the apartment and set it on fire, causing Lenore to have a critical heart attack. Cardenes fled from being startled by a cuckoo clock, and Medina chased after him. A deliveryman named Jimmy Walp came upstairs and saw Lenore still tied, raping her badly enough she was killed from a second heart attack. Cardenas was afraid to go back and made Medina run with him to not get caught.
Detectives swiftly caught and arrested them and another hoodlum they were selling Lenore's diuretics to. Cardenas was told to stay silent by Medina so Medina could be in charge of legal proceedings, taking the most benefit for himself. Since Special Victims wanted the rapist and murderer of Lenore, they took samples from both kids, but neither matched. Cardenas was hassled and beaten in jail, so detectives wanted to give him a deal of no jail time to provide information on the third criminal. Medina swooped in and took the deal, discouraging Cardenas from accepting. When Medina identified the rapist and murderer, Jimmy Walp, he was served allocution papers. However, when Medina was revealed to have caused one of Lenore's two fatal heart attacks, it's left unknown what Cardenas' fate is if he testified against Medina for additional charges. (SVU: "The Third Guy")