Some interesting comments on here which I find mostly to be about human relationships and dare I say it, CRM. The relationships aspect is very difficult since even the suggestion to some drinkers that they are affected by their intake can cause instant and aggressive denial, in any line of work.
Add to that a possible attitude from managers that the reporter is a troublesome employee and from colleagues that he/she is a tell-tale, then there is no wonder that the subject has caused so much discussion and different solutions.
Given the above concerns and that the primary concern should be the safety of the aircraft and passengers, perhaps the best answer would be a mandatory breath test for crew before signing onto a flight.
If the test is carried out before the person officially becomes crew, then no offence would have been caused and they would be prevented from joining the crew. This I think is important given the penalties that can be involved, who wants to see their pilot carted off by the local gendarmerie? Technically, I may be incorrect in that the crew members have been rostered but that is a legal point probably outside of the discussion.
A mandatory test removes all onus on colleagues from having to make difficult decisions that may affect their working relationships. The only person affected would be the person detected as incapacited by alcohol and that would be an objective measurement and not subjective. There is also the advantage of the deterrent effect of such a test. Clearly, if the person has a personal problem, that lies within the realm of the companies HR staff to address.
Finally, just to recognise that the problem of impairment of crew would not be completely solved, there has been no mention of drugs. I'm not concerned only with "social" drugs, but even some widely used drugs like anti-histamines can have debilitating affects on the taker. How many persons would declare themselves unfit because the bottle said "may cause drowsiness" I wonder?
Finally, finally, I am not aircrew, just trying to stand back and put across a different slant on things.