COLE, J., delivered the opinion of the Court.

Because a specific type of impeachment testimony placed in evidence by the State over defendant's objection egregiously impaired his ability to present his defense, we shall, in this case, reverse the defendant's conviction for murder and set aside his sentence of death.

Timothy Clyde Poole was convicted of premeditated murder, felony murder, robbery with a dangerous weapon, and use of a handgun in a crime of violence by a jury in the Circuit Court for Calvert County. This same jury next sentenced him to suffer death. In addition to the death penalty, Poole was sentenced to life imprisonment, twenty years (concurrent), and fifteen years (consecutive). Because Poole was sentenced to die, all of his convictions and sentences are directly reviewable by this Court. Maryland Code (1957, 1976 Repl. Vol., 1980 Cum. Supp.), Article 27, § 414.

The parties have set forth the circumstances giving rise to the charges in the following statement of facts:

David Creel, an eighteen year old student, was working at MacLarty's Pharmacy on the evening of October 22, 1979. According to Creel, at about eight o'clock that evening, two black men came into the store. One put a mask over his head as he walked down some steps to the backroom where Dr. David MacLarty was preparing prescriptions. The other (identified by Creel as Appellant) walked up to Creel who was behind a counter and pointed a shotgun at him. The man, not wearing a mask, told Creel to lock the front door. Creel walked to the front door with the gunman holding his belt and pointing the shotgun at his head.

After the man watching Creel had closed and locked the front door, Creel heard two shots fired in the backroom. Dr. MacLarty said "Is there anyone else out there?" The gunman ordered Creel to say no and then forced Creel to walk ahead of him into the backroom where they found the masked man (Steven Horad) lying on the floor breathing hard and with a head wound. Dr. MacLarty stood by the safe.

Creel's assailant stepped in front of him and shot MacLarty in the chest with a shotgun. MacLarty fell to the floor and lay there, having trouble breathing. Creel was ordered to get the money. The assailant picked up a gun lying beside MacLarty and pointed it at MacLarty's head. Creel said "You don't have to do that." The man, holding the gun an inch from MacLarty's face, pulled the trigger twice without result. Creel surrendered about $150 to the assailant who left the premises. Both MacLarty and Horad later died.

Mark Blob recalled that at about the time of the shooting he and some friends were sitting on a curb in the vicinity of MacLarty's when he noticed three black men drive slowly by in a "late `60's" silver Cadillac with a black vinyl roof. Blob remembered the incident because the men in the car were "looking at us, looking at us real hard." On March 25, 1979, Blob participated in a photographic identification procedure wherein he selected two photographs as looking "like" the men in the car. The photographs selected were of Appellant and David Brown (unrelated to this case). Blob identified Horad as the man sitting in the back seat.

Two address books were taken from Horad's pocket. In one of these, containing a hundred or so listings, was the name "Poole" with two telephone numbers.

When told of the shooting incident the next day, Appellant showed "no reaction whatsoever." Appellant also said that he had not seen Horad since the afternoon of the day of the shooting. Further, Appellant said that at the time of the shooting he was with his girlfriend, Jennifer Lanier, and her roommate, Tamara White, at 3-H Neptune Court in Baltimore County.

At the time of the shooting Appellant was signed out of his residence at "Dismas House" on a six hour pass for 3-H Neptune Court.

Both Tamara White and Jennifer Lanier denied that Appellant had been at 3-H Neptune Court on the evening of the shooting. Lanier also testified that she knew that sometimes Appellant used her address as a "sign out" location but went other places. Lanier did not recall ever having seen Appellant operating an automobile. White, however, said she remembered having seen Appellant operating a large "darkish gray" car of undetermined vintage.

Yvonne Bethea testified for the defense. Bethea stated that on the evening of the shooting Appellant was at her residence at 1604 East Monument Street (about a "ten minute walk" from Dismas House) helping her with school work with which she was having difficulty. (Appellant was a student at Morgan State University at the time of the incident at MacLarty's Pharmacy.)

Poole has raised eight issues in this appeal; however, because of the disposition we make of his fifth issue it will be unnecessary for us to address any of the other issues in detail.

Poole contends the trial court committed reversible error in allowing the State to impeach its own witness, thereby prejudicing his defense and depriving him of a fair trial. He maintains the trial court permitted the State to violate the so-called witness "voucher" rule.

There exists in this State the general rule that a party who produces a witness in court vouches for that witness' credibility and trustworthiness, and no direct attack upon his veracity should be made by the producing party in the absence of surprise, hostility, or deceit. Patterson v. State, 275 Md. 563, 570, 342 A.2d 660 (1975); Proctor Elec. Co. v. Zink, 217 Md. 22, 32, 141 A.2d 721 (1958). Recourse to the right to impeach in such circumstances is strictly limited to those cases in which the party calling the witness has been misled and surprised, or entrapped, to his prejudice. Fleming v. Prince George's County, 277 Md. 655, 678, 358 A.2d 892 (1976); Green v. State, 243 Md. 154, 157, 220 A.2d 544 (1966); Bruce v. State, 218 Md. 87, 95, 145 A.2d 428 (1958). To avoid prejudice, a trial court may, in the exercise of its sound discretion, permit a party to impeach its own witness upon a showing (1) that the calling party is surprised; (2) that the witness' testimony is contrary to prior statements made by this witness to a party, his attorney, or a person to be communicated to them; and (3) that the statement involves facts material to the case. Fleming v. Prince George's County, supra, 277 Md. at 677; Sellman v. State, 232 Md. 344, 348, 192 A.2d 788 (1963). Central to the operation of the exception, however, is the element of prejudice. It is not sufficient to show that the evidence of the witness is not beneficial to the calling party, or that it disappoints his expectations, even though justified. Fleming v. Prince George's County, supra, 277 Md. at 678-79; Travelers Ins. Co. v. Hermann, 154 Md. 171, 179-80, 140 A. 64 (1928).

It is only when all of the above requirements have been met that the trial court, in its discretion, may allow the surprised and damaged party to examine the witness in order to establish the fact that the witness has made a prior statement inconsistent with his present statement from the witness stand. Proof of the prior statement is permitted, not for the purpose of impeaching the general character of the witness, but rather to show why the party has called him. The purpose of this showing is to protect the party who has put him on the stand. Fleming v. Prince George's County, supra, 277 Md. at 678; Green v. State, supra, 243 Md. at 157; Murphy v. State, 120 Md. 229, 233, 87 A. 811 (1913); Smith v. Briscoe, 65 Md. 561, 568-69, 5 A. 334 (1886).

It is within this framework that the witness may be cross-examined by the calling party as to his prior contradictory statement, and, if the witness denies having made the statement, the calling party may offer independent proof thereof. Patterson v. State, supra, 275 Md. at 571; State, use of Chenowith v. Balto. Contracting Co., 177 Md. 1, 15, 6 A.2d 625 (1939). Such proof, however, is not substantive evidence; its only evidentiary effect is to impeach the credibility of the witness. Id.

In the instant case, the determinative issue arose out of the following factual setting. The State established that on October 22, 1979, Poole signed out of Dismas House, the half-way correctional facility where he resided, and gave Lanier's address as his destination. The State produced Detective March who testified that Poole told him he was with Jennifer Lanier and Tamara White, at their house, on the night of the shooting. However, when White took the stand, she testified that Poole had not been there. Lanier, the State's final witness, also testified that Poole was not there the night Horad and MacLarty were shot.

Poole contended at trial (and the State's witness, Lanier, admitted) that it was common practice for him to sign out for Lanier's house when in fact his destination was elsewhere. Thus, when confronted by police the morning after the shooting, it may have been natural for him to say he was at Lanier's house so that his story would be consistent, not only for the police, but also for the officials at Dismas House. However, Poole's alibi was not that he had been with Lanier the night of the shootings, but rather that he had been with Yvonne Bethea (his sole witness, upon whom he rested his entire defense) helping her with homework at her house. Yvonne Bethea so testified.

It is with this backdrop that we analyze the impact of the prosecution's examination of Jennifer Lanier, the State's final witness:

Nevertheless, the State contends, Poole's statement to Lanier constituted an "admission by conduct," and as such, is not excludable as hearsay, but is independently admissible as substantive evidence. What the State overlooks is that it is not Poole's statement with which we are concerned. It is Lanier's prior, out-of-court statement which is at issue here. Thus, even if Lanier had been properly examined on direct, her prior, unsworn statement would not have been admissible to prove the existence of Poole's statement, which was contained therein.

In Green v. State, supra, no error was found in allowing the State to impeach its own witness on the basis of surprise; however, treating the witness' prior inconsistent statement as having substantive value on the issue of the defendant's guilt or innocence was held to constitute prejudicial error. On this basis, Green's conviction was reversed. Thus, even where surprise is shown, "[p]rior statements produced at the trial to show the party calling the witness has been surprised by the witness' testimony, and why the witness was called, are not probative evidence on the merits and are not treated as having any substantive or independent testimonial value." 243 Md. at 158.

The State's rejoinder is that, in any event, Lanier's statement that Poole had told her to say that he had been at her house was harmless as merely cumulative to other evidence which tended to show that Poole was not with Lanier on the night of the shootings. We disagree. This statement is more than just cumulative to White's and Lanier's testimony; it cuts far deeper. This evidence permitted the jury to infer not only that Poole was not at Lanier's house, but also that he had done something that night, the fact of which he wanted to hide and for which he needed to invent an alibi. It permitted the jury to infer that Poole had no innocent explanation for his whereabouts — that he had gotten himself involved in some kind of serious trouble.

It is also apparent to us that Lanier's prior statement cast a shadow over the credibility of Yvonne Bethea. If the jury believed Poole attempted to persuade Lanier to lie, might not they also conclude that Bethea's testimony was perjured? Without Lanier's prior statement Poole had, at least, the opportunity to present to the jury a defense untainted by the suggestion that he had a propensity to tamper with witnesses. We find that the admission of Lanier's statement was fraught with prejudice. Because of this error, the judgments must be reversed and a new trial granted.

While the disposition we make of Poole's fifth issue makes it unnecessary to address the other points raised, we believe that since a new trial must be had it will be of some guidance to the trial court to make two observations with respect to the sentencing phase of a capital case.

First of all, Article 23 of the Maryland Declaration of Rights provides:

In the trial of all criminal cases, the Jury shall be the Judges of Law, as well as of fact, except that the Court may pass upon the sufficiency of the evidence to sustain a conviction.

This provision applies to the trial stage of the proceeding and refers explicitly to the evidence necessary to sustain a conviction. It does not apply to the jury's role in a sentencing proceeding. See Stevenson v. State, 289 Md. 167, 423 A.2d 558 (1980).

Secondly, we strongly discourage any comment by counsel in their arguments to the jury concerning appellate review of a death sentence. Such comments have no relevance to the jury's duty of determining the existence of the various aggravating and mitigating factors, and in deciding whether, upon balancing these factors, a death sentence should be imposed; rather, they tend to encourage the jury to believe that it can shift part of its responsibility to another body. We view such arguments as improper. See Shoemaker v. State, 228 Md. 462, 180 A.2d 682 (1962); see also Moore v. State, 240 Ga. 807, 243 S.E.2d 1, cert. denied, 439 U.S. 903, 99 S.Ct. 268, 58 L.Ed.2d 249 (1978); State v. Berry, 391 So.2d 406 (La. 1980); State v. Jones, 296 N.C. 495, 251 S.E.2d 425 (1979); State v. Gilbert, 273 S.C. 690, 258 S.E.2d 890 (1979).

Judgments of the Circuit Court for Calvert County reversed and case remanded to that court for a new trial.