The attorney for the Commonwealth shall not be present at any time while the special grand jury is in session except that during the investigatory stage of its proceedings he may be present. When the special grand jury is impanelled upon motion of the court or recommendation of a regular grand jury, he may be present during the investigatory stage only when his presence is requested by the special grand jury and may interrogate witnesses provided the special grand jury requests or consents to such interrogation. When the special grand jury was impanelled upon his request, he may examine any witness called to testify or produce evidence, but his examination of a witness shall in no way affect the right of any grand juror to examine the witness.

The attorney for the Commonwealth shall not be present during or after the investigative stage of the proceedings at any time while the special grand jury is discussing, evaluating or considering the testimony of a witness or is deliberating in order to reach decisions or prepare its report, except that he may be present when his legal advice is requested by the special grand jury.