adj. Derived from the term "bloody-hand", which was one of four kinds of offences in the king's forest, by which the offender is supposed to have killed a deer. In Scotland, in such like crimes they say "Taken in the fact, or with the red hand".
- Thomas Blount's Law Dictionary and Glossary, 1717

In modern times, this term refers to catching someone in the act of doing something they aren't supposed to do.

The exact moment of seeing a person doing illegal acts.

When someone is striked on their (often bare) back with the palm of the hand, leaving a red imprint or red hand on their back. Can be done in the changing rooms or any other opportunity

When a young Mexican boy reaches the bottom of his most recent bag of Hot Cheetos and the spicy Cheeto powder coats his little brown digits.

When you finger a girl whilst on their period

1. one who is caught red-handed.
2. a murderer.

When you finger a girl on her period then proceed to masturbate with the same hand without cleaning off her period blood