Idunno
You can tell that just by sense of smell?
Well someone obviously could smell booze (or what they thought was booze) on the guy - and they did the correct thing - handed it over to the cops to sort out.
This is what we pay the cops for - if someone is over the limit, then it is for them, and them alone to take action.
I assume that the guy was over the limit as he has been arrested and charged?
Flaps One
I note that the BALPA web-site does not talk about 'random testing' - only 'peer intervention'.