Identification through the “mortal bullet.”] Vital to the identification of Sacco and Vanzetti as the murderers was the identification of one of the fatal bullets as a bullet coming from Sacco’s pistol. The evidence excluded the possibility that five other bullets found in the dead bodies were fired either by Sacco or Vanzetti. When Judge Thayer placed the case in the jury’s hands for judgment, he charged them that the Commonwealth had introduced the testimony of two experts, Proctor and Van Amburgh, to the effect that the so-called fatal bullet _went through Sacco’s pistol_.[1] Such was neither the belief nor the testimony of Proctor, who refused to accede to this view. In the course of the preparation of the case, District Attorney Katzmann knew that such was not intended to be his testimony. These startling statements call for detailed proof. Proctor, at the time of his testimony, was head of the State Police, and had been in the Department of Public Safety for twenty-three years. On the witness stand he was qualified at length as an expert, who had for twenty years been making examination of and experiments with bullets and revolvers, and had testified in over a hundred capital cases. His testimony was thus offered by the State as entitled to the greatest weight. If the jury could be convinced that the bullet found in Berardelli’s body came out of Sacco’s pistol, the State’s case was invincible. On this _crucial_[1] issue, Captain Proctor testified as follows at the trial: Q. “Have you an opinion as to whether bullet number 3 (exhibit 18) was fired from the Colt automatic which is in evidence (Sacco’s pistol)?” A. “I have.” Q. “What is your opinion?” A. “My opinion is that it is _consistent with_[1] being fired from that pistol.” At the trial, in his closing argument, the District Attorney told the jury: “_You might disregard all the identification testimony and base your verdict on the testimony of these experts._”[1] In the Court’s charge to the jury, Judge Thayer interpreted the evidence to mean that: “_It was his (Sacco’s) pistol that fired the bullet that caused the death of Berardelli. To this effect, the Commonwealth introduced the testimony of two witnesses, Messrs. Proctor and Van Amburgh._”[1] Naturally, the court’s _misleading_[1] interpretation became the jury’s....