The methods that may be used to impeach credibility are subject to Pa. R.E. 401, which defines relevant evidence. For example, the United States Supreme Court held that the Federal Rules clearly contemplated that evidence of bias could be used to impeach credibility even though nothing in those Rules specifically covered the subject. The Court pointed to F.R.E. 401, defining relevancy, and F.R.E. 402, providing for the admissibility of all relevant evidence, in support of its holding. R.E. 401 and 402 are similar to their Federal counterparts, and they, too, support the impeaching of credibility by any means having any tendency to cast doubt on the witness' testimony.
Impeachment evidence is also subject to Pa.
R.E. 403, which provides that relevant evidence may be excluded if its probative value is outweighed by the danger of unfair prejudice. In addition, Pa. 5918, which prohibits, with certain exceptions, the questioning of a defendant who testifies in a criminal case for the purpose of showing that the defendant has committed, been convicted of or charged with another offense or that the defendant has a bad character or reputation. Since the credibility of any witness depends upon his or her powers of perception, capacity to remember, ability to communicate accurately and honesty or integrity, it may always be attacked by showing shortcomings in any of those areas. Where Legal Research Begins On The Web.