catch (someone) red-handed

to discover someone doing something illegal or wrong.

I caught him red-handed trying to break into my car. (often + doing something)

• on the case
• on the cheap
• on the contrary
• on the cutting edge
• on the cutting edge of
• on the cutting edge of something
• on the cutting room floor
• on the dot
• on the double
• on the edge
• on the face of it
• on the face of the earth
• on the factory floor
• on the fast track
• on the fence
• on the firing line
• on the fly
• on the fritz
• on the front burner
• on the front line of
• on the front line of something
• on the front lines of
• on the front lines of something
• on the heels of
• on the heels of something