catch someone red-handed

catch (one) red-handed

To see, and perhaps apprehend, someone as they are doing something (often something nefarious). The phrase might have originally referred to blood on a murderer's hands. The police caught the robbers red-handed as they ransacked another house. Timmy tried to get into the cookie jar again, but I caught him red-handed.
See also: catch
Farlex Dictionary of Idioms.

catch someone red-handed

COMMON If you catch someone red-handed, you see or find them while they are doing something illegal or wrong. The burglar was on the roof and was caught red-handed by the police. They all pleaded guilty to conspiring to import drugs after being caught red-handed by customs officers. Note: The reference here is to a guilty person whose hands are covered in blood.
See also: catch, someone
Collins COBUILD Idioms Dictionary, 3rd ed.
See also:
  • catch (one) red-handed
  • catch red-handed
  • catch somebody red-handed
  • caught red-handed
  • caught in the act
  • catch somebody in the act
  • catch in the act
  • catch (one) in the act
  • catch (one) (doing something)
  • catch it
References in periodicals archive
"So even if you catch someone red-handed for putting something to reuse you cannot book him because there is no law that prohibits it," Peesapaty said on Friday while delivering a lecture organised by Central Research and Training Laboratory (CRTL), the research wing of National Council of Science Museums (NCSM).
It's not my proudest moment, but when you catch someone red-handed you kind of want to retaliate.
"All we have to do is get one or two or three big cases where we catch someone red-handed, and suddenly the targeting policies at these intelligence agencies will start to change."
"The police have been sympathetic, but they are pretty powerless unless they catch someone red-handed. But something needs to be done.