Sometimes you have to ask a different way...

Part of my job is to find out what drugs people were on before admission, including the social ones,

Me: Do you drink alcohol?

P: No

I'm looking at this guy and thinking, "You look like you might to me."

Me: Are you sure?

P: Yes

Me: So no beer or spirits or wine

P: No

Me: Not even at Christmas or at parties?

P: Oh, you mean besides since I was admitted?

Me: Yes

P: Oh well I have the occasional drink

Me: ?

P: A slab (For the non-Aussies that's about 36 cans.)

Me: A slab? How long does that last?

P: ?

Me: How often do you buy a slab?

P: Lunch-time and on the way home from work.

Me: Every day?

P: (Short pause.) Sometimes I get an extra one at the week-end for the missus.