18 Pa.C.S. § 5125

A person commits a misdemeanor of the third degree if, having been required by virtue of any legal process or otherwise to attend and testify in any prosecution for a crime before any court, judge, justice, or other judicial tribunal, or having been recognized or held to bail to attend as a witness on behalf of the Commonwealth or defendant, before any court having jurisdiction, to testify in any prosecution, he unlawfully and willfully conceals himself or absconds from this Commonwealth, or from the jurisdiction of such court, with intent to defeat the end of public justice, and refuses to appear as required by such legal process or otherwise.