I'm just an interested passenger so I can't really understand this issue even arising. The question I asked on a similar topic about a BA pilot a few weeks ago was never really answered so here goes again.....
IF this chap is guilty - or just thinking about other proven cases in the past - the crews concerned must be aware that they are over the limit.
The limit is so low that if a security guard or anybody else for that matter suspects they have been drinking then they surely must be well over the very low tolerance levels allowed. Why don't they just call in sick?
OK, this would cause serious hassle for all concerned arranging a relief crew etc and delayed departures, but holding up in a hotel room for a few hours must be referable to throwing it all away? I know this would be dishonest but surely it's better than losing your job, possibly a lifetimes work or worse.