More specifically, how was he able to hide a cyanide pill while under Allied custody? I'm certain he was thoroughly searched. I heard a rumor about having a cyanide tooth. Is this true?
It's somewhat of a mystery, confounded even more by the fact that for a long time many American veterans present at the Nuremburg trials kept coming forward claiming they were the one to have slipped Goering the cyanide.
One recently* claimed his German girlfriend (a Nazi sympathiser) gave him a fountain ink cartridge filled with what she claimed was medicine. Here: http://www.theguardian.com/world/2005/feb/08/usa.secondworldwar
The official story is that the capsule was hidden in a jar of hair cream. Goering convinced an American gaoler to retrieve the jar from his luggage, removed the pill, then kept it hidden until the night before his execution.
*Well, 10 years ago.