Beth Darnell (Stefanie Tepley) is a hidden villainess from "What Happens in Vegas Dies in Boston", episode 4.07 of Crossing Jordan (airdate November 7, 2004). She was the teenage sister of Amanda Darnell, a young girl who confessed to the brutal murder of Jefferson Mills. While Amanda was being interrogated, Beth was shown outside the interrogation room, comforting her distraught mother.
But as revealed towards the end of the episode, Beth was the true killer, having beaten Jefferson to death with her field hockey stick. The sadistic teen later snapped Jefferson's bones and pulled out some of his teeth as a trophy. To cover her tracks, the evil Beth broke Amanda's arm and ordered her to claim she had killed Jefferson, threatening to kill their dog Shirley if she didn't.
Beth's villainous reveal came when a box of animals she had previously killed was found. When one of the dead squirrels was shown to have blood in its mouth (from where it bit Beth before she killed it), Lily Lebowski did a search of rabies vaccinations and found that Beth had been vaccinated the previous year, exposing her twisted secret.
DA Renee Walcott later questioned Amanda, with Beth and Mr. Darnell watching from outside the room, and claimed she had told them the truth about Beth. In reaction, Amanda pleaded with Beth that she hadn't told anyone and begged her not to hurt Shirley. Shocked by her daughter's actions, Mr. Darnell confronted Beth, who feigned innocence before viciously challenging her father to do something to her. When Mr. Darnell grabbed Beth, the villainess surprised him by twisting out of his grip. Beth was arrested, and the hockey stick she used to kill Jefferson was found in her school locker, along with Jefferson's teeth. Amanda also revealed (offscreen) that Beth confessed to enjoying the sound of Jefferson's bones breaking, revealing her as a sadistic murderer.