Impeachment of defendant by prior conviction is a legal procedure used by prosecutors to discredit a defendant’s testimony in a criminal trial. It is a way of showing that the defendant has a prior history of criminal behavior, which can be used to argue that the defendant is not a credible witness and therefore should not be believed. The two types of impeachment of defendant by prior conviction are (1) direct impeachment, which involves introducing evidence of the defendant’s prior criminal convictions to the jury; and (2) indirect impeachment, which involves introducing evidence of the defendant’s prior bad acts, such as prior criminal behavior, to the jury. In either case, the jury can consider the evidence to determine whether the defendant’s testimony should be believed or not.