JACKSON, Miss. — On a Saturday night in October 1995, a blue Toyota came hurtling down the wrong side of a county road in North Mississippi and crashed head-on into a pickup truck. Scotty Plunk, the driver of the truck, was killed. The driver of the Toyota, 19-year-old Joel Vann, had been drinking so much that he did not remember the accident.

Mr. Vann pleaded guilty to “D.U.I.-death,” and in lieu of jail attended a residential treatment program. This month he was one of 198 people pardoned by Mississippi’s governor, Haley Barbour, as he left office.

It is unclear what persuaded the governor to pardon Mr. Vann; his clemency application contains glowing references and a case study. But the letter to the governor from Mr. Vann’s father, the brother-in-law of a former Republican state committee member and contributor to Mr. Barbour, had a familiar tone.

“All is well in Corinth, and as you may know, we have two new Republican aldermen,” the letter said. It traced Mr. Vann’s path from rehabilitation through college, marriage and fatherhood before asking for “your consideration to grant Joel a pardon at the most appropriate time.”