Dictionary.net

• Having hands red with blood; in the very act, as if with red or bloody hands; - said of a person taken in the act of homicide; hence, fresh from the commission of crime; as, he was taken red-hand or red-handed.

2010 - New Age Dictionary Database
By Oddity Software

• Having hands red with blood; in the very act, as if with red or bloody hands; - said of a person taken in the act of homicide; hence, fresh from the commission of crime; as, he was taken red-hand or red-handed.

1913 - Webster's Revised Unabridged Dictionary
By Noah Webster.