Danny Surratt, 62, had 20 years with the department and was working there at the time of the assault in 2010.
Prosecutors said his DNA was found inside the victim’s underwear.
The jury deliberated about six hours before returning the verdict late last Friday.
“The victim in this case had her innocence ripped away by someone she trusted, but she was brave enough to stand up to him in a court of law,” Ninth District Attorney Matthew Chandler said in a statement released to the news media. “We are so proud of her for staying strong.”
The rapist faces 18-years in prison for in this case, but his troubles don’t end there.
He’s also facing a trial for raping the girl’s 16-year-old sister.