OKLAHOMA CITY — A “serial rapist with a badge” who now faces many years in prison for raping black women on his beat was caught because of the courageous actions of a grandmother who he pulled over and sexually assaulted, her lawyer said Friday.

“He just picked the wrong lady to stop that night,” said Jannie Ligons, who filed a police complaint and then called a local TV station to share her experience, triggering an investigation that led to charges that Daniel Holtzlaw assaulted 13 women while working as an Oklahoma City police officer.

The conviction of Holtzclaw Thursday night on charges of rape, sexual battery and other charges should send a strong message nationwide, said attorney Benjamin Crump, who is seeking civil damages from the city for some of the victims.

“Black women’s lives matter. It just as if this were a group of 13 white women.”

Jurors found Holtzclaw, who turned 29 on Thursday, guilty of 18 counts involving eight of the women, and acquitted him of charges involving five other women he met on his beat in a minority, low-income neighborhood, and recommended 263 years, including 30-year sentences for each of four first-degree rape convictions.

Flanked by her family, other victims and a group of African-American activists outside the Oklahoma City courthouse, Ligons said she knew she had done nothing wrong when the officer pulled her over and assaulted her.