To catch someone out means to cause them to make a mistake that reveals that they are lying about something, do not know something, or cannot do something. [mainly British]
Detectives followed him for months hoping to catch him out in some deception. [V n P prep]
He did not like to be caught out on details. [V n P prep]
The government has been caught out by the speed of events. [be V-ed P + by]