Michael Dane Ward, 45, faces a possible life sentence for the crimes, which involved oral copulation, sodomy and lewd acts on children under the age of 10, the Los Angeles County district attorney's office said in a statement.
The victims were a boy and girl, prosecutors said.
Ward, whose work with the Sheriff's Department had involved advising and training law enforcement officers, was relieved of duty when he was arrested by the Sheriff's Department's Special Victims Bureau last year. The assaults were unrelated to his job, officials said.
The boy and girl, who were assaulted between October 2013 and November 2015, testified against Ward at trial. Jurors deliberated for three days before finding Ward guilty of four counts of lewd acts on a child, two counts of forcible lewd acts on a child under 14, three counts of oral copulation of a child 10 years old or younger and one count of sodomy with a child under 10.
Both children were under the age of 10 at the time they were assaulted, according to the district attorney's office.
Ward's attorneys did not return calls or e-mails for comment Friday afternoon.
Ward, of La Cañada-Flintridge, is expected to be sentenced Oct. 19.