At a traffic safety conference in 1980, a Californian named Candy Lightner delivered her first public speech about a 13-year-old freckle-faced girl who had recently been killed by a drunk driver with several previous convictions.

At the conclusion of her talk, she announced, “That girl was my daughter.”

As Lightner later wrote, the press ran out of the auditorium to call their photographers. “Pandemonium ensued,” she recalled.

Recidivist drunk drivers had killed children—and adults—for decades in the United States, often receiving little …