“ Prejudice ensues from a denial of the opportunity to place the witness in his proper setting and put the weight of his testimony and his credibility to a test, without which the jury cannot fairly appraise them. * * * To say that prejudice can be established only by showing that the cross-examination, if pursued, would necessarily have brought out facts tending to discredit the testimony in chief, is to deny a substantial right and withdraw one of the safeguards essential to a fair trial. ”

“ It may exercise reasonable judgment in determining when the subject is exhausted. * * * But no obligation is imposed on the court, such as that suggested below, to protect a witness from being discredited on cross-examination, short of an attempted invasion of his constitutional protection from self incrimination, properly invoked. There is a duty to protect him from questions which go beyond the bounds of proper cross-examination merely to harass, annoy or humiliate him. ”

“ But the petitioner was denied the right to ask the principal prosecution witness either his name or where he lived, although the witness admitted that the name he had first given was false. Yet when the credibility of a witness is in issue, the very starting point in 'exposing falsehood and bringing out the truth' [7] through cross-examination must necessarily be to ask the witness who he is and where he lives. The witness' name and address open countless avenues of in-court examination and out-of-court investigation. ”