Today's idiom is the first of the New Year. Hope you enjoy it!
"Catch someone red-handed"
When you see some some doing something wrong or illegal.
Example 1
The shop owner saw the girl put something in her pocket without paying for it. He caught her red-handed .
Example 2
A. The police caught the thief red-handed .
B. How?
A. They saw him break the window.
https://idioms.thefreedictionary.com/catch+red-handed