Pennsylvania Rule of Evidence 609 pertains to when a witness may be impeached with a prior conviction. Pennsylvania allows for either party, in a criminal case, to impeach any witness with a select category of prior convictions. In Pennsylvania, this select category of prior convictions is known as "crimen falsi." Crimen falsi means crimes involving dishonesty. In order for a crime to be classified as crimen falsi, the offense must involve some element of deceit or dishonesty, ie theft or forgery.
Pennsylvania law permits either party to introduce the use of expert testimony during trial, so long as the party complies with the rules of evidence. The party must first assert that an expert is needed to give the type of testimony and evidence sought to be admitted. Stated in other words, a court will only allow the testimony of an expert witness, if the testimony calls for scientific, technical, or other special knowledge, which a lay witness would be unable to testify. Therefore, the party must show that there is an issue at trial that can only be resolved by that expert witness' testimony.
Pennsylvania Rules of Evidence allow a party to confront a witness with that witness's prior inconsistent statements. The purpose of confronting a witness with a prior inconsistent statement is to attack that witness's credibility. Often times this is done when a witness has given statements to the police and preliminary hearing testimony which differs from the witness's trial testimony.
Under Pennsylvania Rules of Evidence, during trial, either party may attack the credibility of any witness with evidence that the witness has been convicted of a crime involving dishonesty or false statement. Generally, the conviction or the date of release from confinement, whichever is later, must be within 10 years from the date at which the witness is being impeached.
The Pennsylvania Supreme Court recently held that the defense is NOT permitted to call an expert witness who would testify about "false confessions." Social scientists have spent a number of years studying a phenomenon known as the "false confession."
Under Pennsylvania Rules of Evidence, generally, evidence of a past crime, wrong, or other bad act is not admissible for the purpose of showing that the accused did something bad in his past it is more likely he committed the crime he is presently facing at trial. Stated a different way: it is the general rule that the Commonwealth is not permitted to introduce the defendant's prior crimes or other bad acts for the purpose of showing the defendant committed this present crime or to show "once a criminal, always a criminal."
The central concern of the Confrontation Clause is to ensure the reliability of the evidence against a criminal defendant by subjecting it to rigorous testing in the context of an adversary proceeding before the trier of fact. The word "confront," after all, also means a clashing of forces or ideas, thus carrying with it the notion of adversariness.