The Collaborative International Dictionary of English v.0.48:
imp. & p. p. of Strike.
Struck jury (Law), a special jury, composed of persons
having special knowledge or qualifications, selected by
striking from the panel of jurors a certain number for
each party, leaving the number required by law to try the
Bouvier's Law Dictionary, Revised 6th Ed (1856):
STRUCK JURY. A special jury selected by striking from the panel of jurors, a
certain number by each party, so as to leave a number required by law to try
the cause. In general, a list of forty-eight jurors is made out for each
case; the plaintiff strikes off twelve, and the defendant the same number
from those who remain twelve are to be selected to try the cause, unless
they are challenged for cause. See Challenge.