Spear -- who was fired from the Border Patrol in February after 18 years in law enforcement -- was acquitted of furnishing cocaine to a minor and sexual penetration of an intoxicated person.
The now 18-year-old victim told police that Spear touched her inappropriately in his home and sexually assaulted her in a hotel room after giving her cocaine.
She testified that he "creeped her out" from the moment she met him.
The victim testified that Spear touched her private parts over her clothes while she was sleeping at his home on July 4, 2015.
She said that on Oct. 20, 2015, she and Spear checked into a Mission Bay hotel, where he gave her "a lot of cocaine," then fondled and orally copulated her. She said Spear also took photos of her in lingerie.
About a month and a half later, she said she told her father what had happened and police were called.
Deputy District Attorney Marisa Di Tillio told the jury that the victim got to know Spear because she was friends with his daughter. The girls met through a home-schooling program.
The victim would spend time at the Spear home and the defendant developed his own relationship with her, using sexually charged language and asking her if she was still a virgin, Di Tillio told the jury.
After the night at the hotel, Spear touched the girl's privates after she fell asleep at his home on Halloween night, the prosecutor told the jury. Spear even talked about leaving his wife for the girl, Di Tillio said.
Spear denied the charges on the witness stand.