I'm no Sherlock Holmes

angry doc: … and you should stop smoking too.

Patient: But I don’t smoke!

angry doc: (annoyed) Then what’s that in your shirt pocket?

(Points at cigarette packet in patient’s shirt pocket.)

Patient: This? I only use it to hold my keys. See?

(Produces keys from otherwise empty cigarette packet.)

angry doc: … OK, let’s talk about your diet now…