On December 7, 1977, the defendant was convicted of conspiracy to commit armed robbery of a bank while masked or disguised. He was sentenced to a term of imprisonment not exceeding ten years nor less than seven years. This court heard the defendant’s appeal in
Commonwealth
v.
Liebman,
After the district attorney applied to the Federal District Court for release of the testimony, the Federal court transmitted the grand jury testimony of these two witnesses to the Superior Court. The judge then made the testimony available to both parties. On the defendant’s motion, the judge held a hearing to consider the potential effect the absence of these Federal grand jury minutes had on the defendant’s trial. The judge concluded that this testimony “could not create a reasonable doubt that did not otherwise exist.
Commonwealth
v.
Liebman,
[
1. The prior proceedings. The two principal prosecution witnesses at the defendant’s trial were Milton Schnapf and Deborah Hahn who testified to the following facts. The defendant, Richard H. Liebman, a Massachusetts attorney, had performed occasional legal services for Schnapf and later participated in Schnapf’s business operations which involved ownership of fast food restaurants. Early in 1975, the defendant suggested that Schnapf add Stanley Ulatowski, a paroled bank robber, to the payroll of one of the restaurants. The three men then planned a bank robbery which was executed by Ulatowski and two other men on February 26, 1975. Deborah Hahn, a manager of one of Schnapf’s restaurants, was brought into the conspiracy to provide Ulatowski with an alibi at the time of the robbery. *485 Both Hahn and Schnapf testified to meetings and conversations with the defendant both before and after the robbery.
Ulatowski was arrested the week after the robbery. 1 Schnapf fled to Florida on March 9, 1975. On March 11, Hahn was called before a Federal grand jury and briefly questioned about her knowledge of the robbery. On May 13, 1975, she was recalled before the grand jury and questioned more extensively about her knowledge of the events preceding and following the robbery. After being arrested in Florida and indicted for his participation in the crime, Schnapf testified before the Federal grand jury on February 19, 1976.
The defendant argues that the Federal grand jury testimony of Hahn and Schnapf contains exculpatory evidence. We have reviewed the testimony of these witnesses both before the grand jury and at trial. A reading of Schnapf’s grand jury testimony reveals, as the judge at the hearing below found, that Schnapf specifically and fully implicated Liebman in the plotting and the concealment of the robbery. Differences between Schnapf’s grand jury and trial testimony involved only matters of detail, such as the precise sequence of meetings between Schnapf and Liebman after the robbery and whether Liebman or Schnapf initiated a telephone call after the robbery.
A comparison of Hahn’s grand jury testimony with her subsequent trial testimony, however, reveals more serious inconsistencies. 2 Near the beginning of each of her appearances before the grand jury Hahn was asked, “Has anyone made any threats against you, or threatened to take any action against you, directly or indirectly, to prevent you from giving testimony before the Grand Jury or causing you to testify in any manner.” She answered, “No,” both times. At the trial, however, she testified to having been threatened *486 several times. She said that on the night following the robbery Liebman told her twice that he and the other conspirators had a lot of friends and that she should say nothing to anyone. During one of these conversations she said that Liebman added that she could “end up getting hurt” if she told the authorities of her knowledge of the robbery. At the grand jury, Hahn testified that she had discussed her prior appearance before the grand jury with Liebman. Although the Federal prosecutor told Hahn she need not disclose communications with her attorney, whom the prosecutor assumed was Liebman, this disclaimer concerning conversations with Liebman came long after the prosecutor asked her if she had been threatened in connection with her grand jury testimony. Therefore the disclaimer does not explain her answer. She also told the grand jury that she first learned of the robbery several days after its occurrence, but at trial her testimony revealed that she knew about the planned robbery before it happened and that she knew about its occurrence and who was involved promptly after the event.
2.
The standard of review.
In
Liebman I,
we recognized that for a defendant attempting to obtain pretrial discovery in a case such as this the presence of “two sovereignties creates a potentiality for unfairness which would need correction if realized in practice.”
Id.
at 674. In this case, this basic unfairness occurred. Despite initiating several legal proceedings,
3
the defendant was unable to obtain access to the Federal grand jury testimony of the two principal witnesses against him at the State trial although the defendant would have been entitled under State law to the testimony if it had been given before a State grand jury.
Commonwealth v. Stewart,
Nevertheless, the general principles set forth in Brady and Agurs for determining “the evidence’s favorable character for the defense” and for evaluating the “materiality of the evidence” are useful in deciding whether the minutes “might create a reasonable doubt that did not otherwise exist.” Liebman I, supra at 676. 4
*488
In
Brady,
the Supreme Court held that “the suppression by the prosecution of evidence favorable to the accused upon request violates due process where the evidence is material either to guilt or to punishment, irrespective of the good faith or bad faith of the prosecution.”
Brady, supra
at 87. In
Agurs,
the Court, in analyzing the holding in
Brady,
stated that “implicit in the requirement of materiality [of the evidence] is a concern that the suppressed evidence might have affected the outcome of the trial.”
Agurs, supra
at 104. This standard of materiality “must reflect our overriding concern with the justice of the finding of guilt. . . . [I]f the omitted evidence creates a reasonable doubt that did not otherwise exist, constitutional error has been committed.”
Id.
at 112. This necessarily requires that the omission of the evidence be evaluated in the context of the entire record.
Id.
at 112-113.
Commonwealth
v.
Ellison,
After reviewing the grand jury testimony and applying the test set forth in
Liebman I,
the judge below concluded that this evidence could not have created a reasonable doubt that did not otherwise exist. We disagree. We believe that introduction of Hahn’s grand jury testimony to impeach her trial testimony might have created a reasonable doubt which did not otherwise exist. Hahn was one of the two major witnesses against the defendant. As we noted in
Liebman I
at 673: “Apart from the testimony of these two
*489
witnesses, there was no case against the defendant.” If Liebman had been in possession of the grand jury minutes at the trial and had made their contents known to the jury, the jury could have found that the grand jury testimony by Hahn that she was not threatened substantially undercut her trial testimony that Liebman told her that he had friends and that she could get hurt if she told what she knew. This coupled with her inconsistent testimony concerning when she first learned of the robbery might have made a difference to the jury. Evidence which impeaches the credibility of a key prosecution witness is exculpatory for the defendant and is clearly material.
Commonwealth
v.
Collins,
Where the Commonwealth’s case depends so heavily on the testimony of a witness we believe that the jury might reasonably have been influenced by this evidence which seriously undermines the credibility of that witness and that a reasonable doubt that did not otherwise exist might have been created in the jurors’ minds. See Agurs, supra at 112-113; Commonwealth v. Collins, supra at 12.
The judge’s otherwise complete and detailed findings attached no significance to these inconsistencies, perhaps because he found that “Hahn’s testimony would also have been an aid to the prosecution.” Our analysis of this finding is colored by the fact that when a judge undertakes to decide if a grand jury transcript benefits the defendant’s case he is “assuming vicariously and uncomfortably the role of counsel.”
Commonwealth
v.
Stewart,
*490 For the foregoing reasons, we conclude that the defendant must be afforded a new trial and we remand the case to the Superior Court with instructions to grant the defendant’s motion.
So ordered.
Notes
He was subsequently tried for the robbery in Federal court, but was found not guilty. He did not testify at the defendant’s trial.
Hahn testified at the trial under a promise that she would not be subjected to State prosecution.
The defendant brought two proceedings in the Federal court and filed a variety of motions in the State court in his attempt to obtain the grand jury testimony.
This is consistent with our statement in
Liebman I, supra
at 676, that “[i]f the minutes might create a reasonable doubt that did not otherwise exist, a new trial may be appropriate.” See
Commonwealth
v.
DeChristoforo,
