Regional Jet 700 ER/LR (CRJ700)
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Distraction
Deviation / Discrepancy - Procedural Security; Flight Deck / Cabin / Aircraft Event Illness / Injury; Flight Deck / Cabin / Aircraft Event Passenger Misconduct
Flight Crew Diverted; General Police / Security Involved
Human Factors; Company Policy
Inside the terminal walking to our airplane we noticed an older man who appeared to be intoxicated. Later we became aware that he was going to be one of our passengers when one of the FA's (Flight Attendant) told us he was on our flight. She alerted us to that he was drunk and that he could not go. As we were discussing this a [Supervisor] comes down to the airplane and told us that the man in question had been communicating with the airport police and the airport police told the [Supervisor] that the passenger in question was not intoxicated; but had been to detox and that was why he acted differently. With this information in hand we saw no reason for why he should be denied the flight. We depart with no issue but halfway through the flight we get a call from one of the flight attendants. The passenger in question had become unruly and had asked for alcohol. He said that if he did not get alcohol he could have a stroke. At this point the FA call was more of an informational call to keep us updated on what was going on in the passenger cabin. 10 minutes later the flight attendant called us again using the emergency call button and then tells us that the passenger stood up and was interfering and was pulling his shirt off. He had also earlier expressed to the passenger next to him that he was considering suicide. As we understood it during the call there was a dead heading pilot and passenger that helped to restrain the passenger.  After the flight attendant call we expeditiously diverted to ZZZ. Authorities and medical assistants met the airplane. The passenger was taken off the airplane. Unruly; unpredictable passenger.It is a hard call. The police said he was not intoxicated. The [Supervisor] relayed the information. We were busy with readying the aircraft for safe flight. We trusted both the Police and the [Supervisor].
CRJ-700 Captain reported an intoxicated passenger; whose erratic behavior in flight resulted in the flight diverting to the nearest suitable airport.