Presley Gerber: Detox Center CEO Says Rehab Patients Showing Up Intoxicated Is Common

Presley Gerber showing up to a sober-living facility while seemingly intoxicated isn't odd, so says an executive in the recovery industry ... and he tells us lots of people are getting a final fix before trying to get clean.

Nick Mathews -- a CEO in the rehab and sober living space -- joined us on "TMZ Live" Tuesday to discuss Presley's shocking death at a Santa Monica rehab facility.

Charles asked Nick if people should be surprised that Presley did not appear sober when he checked in the night before he died.

Nick tells us many addicts are intoxicated when they arrive after one last night of partying, and sobriety isn't always a precursor to getting into a rehab facility.

Basically, there are no laws governing exactly what condition a person needs to be in before they're admitted to the facility ... so some facilities end up admitting intoxicated people.

They're usually patted down for drugs and drug tested, Nick says ... but not all facilities are going to turn away people for doing drugs before they get there.

Plus, Nick explains the difference between the more relaxed sober-living facilities and the more intense detox joints ... and he breaks down the kind of restrictions, or lack thereof, Presley may have been under before he died.

We broke the story ... Presley died from a suspected overdose Sunday morning at rehab facility -- and sources with direct knowledge have told us he was struggling with issues with ketamine, though we've been told a doctor had recently prescribed the drug.