In Pennsylvania, evidence that a witness has a criminal record can, in certain circumstances, be introduced into evidence to cast doubt on a witness's credibility or believability.  Unlike other states and the federal courts, it is not the seriousness of the crime but whether it involves dishonesty or falsity that determines if a court will allow it to be used in a trial.  For example, the charge of shoplifting or retail theft is normally a minor offense but because it involves dishonesty it can be used to attack the credibility of a witness.  On the other hand, first degree murder often can not be similarly used because it normally does not include an element of dishonesty.  The theory of the law is that committing a crime of dishonesty raises serious doubts concerning whether a witness should be believed or not.  The law does not consider the commission of other crimes not involving dishonesty to raise such doubts.