 [ Federal jury selectors ] must not allow the desire for competent jurors to lead them into selections which do not comport with the concept of the jury as a cross @-@ section of the community . Tendencies , no matter how slight , toward the selection of jurors by any method other than a process which will insure a trial by a representative group are undermining processes weakening the institution of jury trial , and should be sturdily resisted . That the motives influencing such tendencies may be of the best must not blind us to the dangers of allowing any encroachment whatsoever on this essential right . Steps innocently taken may , one by one , lead to the irretrievable impairment of substantial liberties . 
