1969 Sole purpose of impeachment is to vitiate a witness' credibility. 1967 Proper time for impeaching credit of witness is after he has been examined. Witness may not be impeached on collateral issue. Whether a matter is collateral within meaning of rule that witness may not be impeached on collateral issue depends on whether direct evidence to establish matter could be introduced. What is collateral matter within meaning of rule that witness may not be impeached on collateral issue depends on issue in case.
Malicious libel enjoys no constitutional protection in any context.