Remember that federal investigations by prosecutors, including special counsels, are by their very nature one sided. They hear only evidence of guilt and not exculpatory evidence. Their witnesses are not subject to the adversarial process. There is no cross examination. The evidence is taken in secret behind the closed doors of a grand jury. For that very reason, prosecutors can only conclude whether there is sufficient evidence to commence a prosecution. They are not in a position to decide whether the subject of the investigation is guilty or is innocent of any crimes.
Read the rest of Alan Dershowitz's column at The Hill.