A person who takes part in the procurement, initiation or continuation of civil proceedings against another has probable cause for doing so if he reasonably believes in the existence of the facts upon which the claim is based, and either: (1) reasonably believes that under those facts the claim may be valid under the existing or developing law; (2) believes to this effect in reliance upon the advice of counsel, sought in good faith and given after full disclosure of all relevant facts within his knowledge and information; or (3) believes as an attorney of record, in good faith that his procurement, initiation or continuation of a civil cause is not intended to merely harass or maliciously injure the opposite party.
Pennsylvania Legal Code