caught somebody red-handed

”caught somebody red-handed”
to catch a person in the act of doing something wrong
مچ کسی را در حین انجام کار نادرستی گرفتن

Example 1: Tom was stealing the car when the police drove by and caught him red-handed.
Example 2: Mary tried to cash a forged check at the bank, and the teller caught her red-handed.