chytit, přistihnout koho při činu, in flagranti, nachytat na švestkách

He was caught with his pants down when he was asked for the figures but was unable to produce them. IC

Apparently he was caught with his pants down. His wife came home to find him in bed with the neighbour. CIDI

He asked me where I'd been the previous evening and I was caught with my trousers down. CIDI