Remanded for an evidentiary hearing. If it appears thereafter that the failure to commence trial within 180 days occurred despite due diligence by the Commonwealth and that the extensions granted by the lower court were *430proper, then appellant’s motion in arrest of judgment shall be dismissed. If, however, it appears that the failure to commence trial within 180 days was caused by a lack of due diligence on the part of the Commonwealth and that the extensions of time, therefore, were improperly granted, then the motion in arrest of judgment shall be granted and appellant shall be discharged.