Pennington was last seen leaving her family's residence on Orchard Drive in Montville, Connecticut during the early morning hours of May 29, 1996. She climbed through her brother's window and planned to meet friends, but she never returned home. Her mother discovered her missing at 5:30 a.m. when she went to wake her for school. The window was left open and one of Pennington's stuffed animals was tucked in the bed.

Pennington is believed to have been picked up by a 15-year-old classmate, Patrick J. "PJ" Allain, and a 30-year-old man, George Leniart, after she left her home. A photograph of Leniart is posted below this case summary. Allain later stated he, Leniart and Pennington went into the woods, drank beer and smoked marijuana that night. He stated he and Leniart had consensual sex with Pennington, then changed his story and said Leniart had raped her and had planned to murder her. Allain told investigators that Leniart dropped him off at his house and left with Pennington, and he did not know what happened to her after that.

Leniart was awaiting trial for raping a teenage girl when Pennington disappeared in 1996; he was later convicted. In 2007, he was convicted of sexually assaulting a teenage boy. Authorities interviewed several witnesses who stated Allain and Leniart murdered Pennington on the night she went missing. Leniart told investigators he knew Allain, but he later denied this. He also denies having ever met Pennington, but it was proven that he called her house five times on the day of her disappearance.

Pennington's mother does not believe her daughter ran away. She stated there was $950 in cash in the house for the family's rent payment on the night Pennington disappeared and Pennington knew where it was, but she did not take it when she left her home. She also took no personal belongings with her, not even her purse. She was originally thought to have taken her black bookbag, but it was later found in her locker at school.

A family friend, Adrian Butler, told authorities that he spoke to Pennington for fifteen to thirty minutes at a Blockbuster video rental store in Virginia Beach, Virginia in 1999. He did not realize that she had been reported missing. Butler stated he did not recognize Pennington until she introduced herself, and that she looked haggard, as if she had been abusing drugs. He said she was accompanied by a toddler while he spoke to her, and that they stopped talking after a man in his late twenties walked into the store and insisted Pennington leave without renting a movie. Butler told the Penningtons about seeing their daughter after they called him three weeks after the alleged sighting. Investigators have since discounted his story.

In April 2008, Leniart, who is still incarcerated on the 2007 sexual assault conviction, was charged with capital murder, kidnapping and sexual assault in Pennington's case. Authorities will not seek the death penalty against him; if convicted, he faces life in prison. Leniart allegedly confessed Pennington's murder to several individuals; he supposedly said he bound and raped her, then killed her because she was screaming. Pennington's body was not been recovered. Leniart was a fisherman at the time of her disappearance and may have dumped it in the ocean. He has pleaded not guilty and is awaiting trial.

Pennington's family moved to Montville in 1994; her father, a mechanic, was transferred to the area by the United States Navy. She enrolled in Montville High School as a freshman. She had been a good student, but her grades began slipping in 1996 and she argued with her parents over it. She also broke up with her boyfriend shortly prior to her disappearance. However, her mother stated she believed her daughter was just going through a normal rebellious phase and was not having any serious problems. Pennington's father has since retired from the Navy and has moved to North Carolina. Pennington's mother believes that her daughter was involved with a rough crowd at the time of her 1996 disappearance. Her mother said that she feared Pennington was sold into prostitution. Foul play is suspected in her case due to the circumstances involved.

Some agencies state that Pennington vanished from Uncasville, Connecticut.

Above: Leniart in 2008