red-handed

from WordNet (r) 3.0 (2006)

red-handed
    adv 1: doing something reprehensible or showing clear evidence
           of having done something reprehensible; "he was caught
           red-handed"
    adj 1: in the act of committing a crime or other reprehensible
           act; "caught red-handed"

from The Collaborative International Dictionary of English v.0.48

Red-hand \Red"-hand`\ (r?d"h?nd`), Red-handed \Red"-hand`ed\
   (-h?nd`?d), a. or adv.
   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]