Marci Riker was the wife of U.S. Navy Commander Dirk Riker, (played by Charles Rocket) the one-time commanding officer of a young Al "Bingo" Calavicci, then an Ensign, then stationed on Torrey Pines Naval Base in 1957, who became his chief nemesis, who accuses him of the rape/murder of her in the Quantum Leap Season Four episode titled "A Leap For Lisa". The part of Riker was played by actress/model Debbie James.
Marci, who had a reputation about her having slept with practically every man that was under her husband Dirks command with the notable exception of Al, suffered with the same character flaw of her husband, who, when he confronted Sam, who leaped into the young Al, or "Bingo", who apparently not only knew of her promiscuous indiscretions, but, like her, got a perverse thrill out of it, and used it as a romantic spark in their love/hate marriage!
Chip tells Sam (as Bingo), who was in the middle of a Court Martial for the death of Marci, and also, without the testimony of Lisa, who originally Vouched for his whereabouts on the night of Marci's death by telling his lawyer, CDR Hobbs, before dying in a car crash later, that he dropped Al and Lisa off at a motel the night of the murder, then drove to the officer's club in Al's car. He saw Riker abusing Marci in the parking lot and gave her a ride. She was drunk and wanted someplace where she could run naked. They had slept together before, and he said he was in love with her. While Marci was undressing he came on to her, but she rebuffed him. Chip tried to force himself on her, but he didn't rape her and then she slipped and fell, striking her head on a rock and dying instantly.
However, When Al (whose existence past 1960 was temporarily erased from existence, when the odds of his conviction and execution went up to 100%, and where he was briefly replaced by Edward St. John V as Sam's guide) meets with his younger self, Bingo, in the leaping chamber and then gets him to leap into himself on the night of Marci's death with the instructions not to let buddy Chip, who he was with before Chip met up with Marci, out of his sight. All of the events, Chip's running into Marci, Riker's wife's death, a distraught over Bingo's being accused of it Lisa's auto accident, and the confrontation with Riker at the Court Martial trial, and the trial proceedings too, were all erased from past history, prevented from ever taking place.