Investigators say a King County sheriff's deputy was impaired by multiple prescription drugs when he was found slumped over the steering wheel of his patrol car on New Year's Eve in a Newcastle parking lot.

The three-month investigation was conducted by Bellevue police who had a blood sample tested at a lab in Pennsylvania. It found the presence of multiple prescription drugs that are dispensed with warnings against operating machinery or vehicles.

The King County prosecutor's office will decide whether to charge the deputy.

The 46-year-old is a 15-year veteran who also faces an internal investigation.