The Supreme Court reasoned that the criterion for excluding a prospective juror for cause in a capital cases is whether the juror's views would 'prevent or substantially impair the performance of his duties as a juror in accordance with his instruction and his oath.' If a judge determines, based upon the juror's responses and demeanor, that the juror's beliefs will 'substantially impair' his or her ability to apply the law, that juror will be excused for cause even though no determination is made as to whether the juror could set aside those beliefs and fulfill a juror's duties. Because the terms of this standard are not readily definable, its adoption will result in varying interpretations and applications among the courts. Until the 'Witt' decision, the Court had recognized that to ensure the capital defendant of an impartial jury trial, a State's power to exclude those prospective jurors opposed to the death penalty had to be limited only to those jurors who would frustrate the State's capital punishment scheme. Under the new standard, jurors could be excluded on the basis that their beliefs might frustrate the State's capital punishment scheme. As a consequence, capital defendants now risk the possibility of a death sentence imposed by a jury biased against them with respect to the penalty. 72 footnotes.