A registered sex offender from Ukiah is facing new charges after investigators say he was caught in an undercover online sting operation. The San Mateo County Sheriff’s Office says 36-year-old Christopher Purtill exchanged explicit messages during conversations tied to a child predator investigation earlier this spring. Detectives, along with Ukiah Police and state parole officers, arrested Purtill near his home on May 7th for violating parole conditions. He’s currently being held in the Mendocino County Jail and is expected to be sent to San Mateo County for prosecution.