It started with a drug raid in Houston and a shootout that left two people dead, five police officers wounded and one of them charged with murder, accused of making up information to obtain a warrant.

Now 69 people whose prosecutions relied on evidence from that accused officer are likely to have their convictions reversed under a process that began on Wednesday, and many more could in the future. The news had echoes of other high-profile police scandals, including the 1990s Rampart case in Los Angeles and the wrongful prosecution of dozens of African-Americans in Tulia, Texas, two decades ago.

Almost all of the 69 defendants have already served their sentences, which ranged from a few months in jail to four years in state prison. They had all pleaded guilty as a result of deals in which prosecutors relied on evidence from Gerald Goines, the narcotics officer who was charged last year with two counts of felony murder for his role in the botched raid.

The chief prosecutor in Houston, Kim Ogg, began a review of all the cases that Mr. Goines had handled. She said on Wednesday that her office had identified 69 defendants going back to 2008 who were prosecuted primarily based on his word. She said those defendants should now be entitled to the presumption that Mr. Goines had lied to obtain the convictions.