OPINION
CAPPY, Justice.This is a direct appeal from the order of the trial court denying appellant’s petition pursuant to the Post Conviction Relief Act (Hereinafter “the PCRA”). 42 Pa.C.S. § 9546(d). (Suspended August 11, 1997, reinstating subsection (d) from the 1988 Act). Appellant alleges that he is entitled to relief under the PCRA, as his conviction resulted from a constitu*459tional violation of due process in contravention of Brady v. Maryland, 373 U.S. 83, 83 S.Ct. 1194, 10 L.Ed.2d 215 (1963). 42 Pa.C.S. § 9543(2)(i). As for the following reasons we find appellant is entitled to relief, we reverse the order of the trial court.1
Our resolution of this case requires that we set forth a brief synopsis of the facts that led to appellant’s conviction. On August 18, 1983, John Henry Strock was driving a white Ford Grenada along Route 81 in Green Castle, Pennsylvania. Mr. Strock stopped the car on the side of the road and offered a ride to two hitchhikers, James Strong, the appellant herein, and James Alexander. According to the trial testimony of James Alexander, Alexander sat in the front seat and appellant sat in the backseat. (Trial Transcript, hereinafter “T.T.” p. 1224). Alexander testified that he promptly fell asleep. (T.T. p. 1225).
When Alexander woke, he observed appellant produce a .20 gauge sawed-off shotgun and rest it upon Mr. Strock’s shoulder. (T.T. p. 1225). Appellant directed Mr. Strock to pull the car to the side of the road and exchange seats with Alexander, so that Alexander could drive the car. (T.T. p. 1226). After driving for some time, Alexander pulled the car to the side of the road along an isolated stretch of interstate 81. (T.T. p. 1227). Alexander walked into the woods a few steps in order to relieve himself. When Alexander returned to the car, appellant and Mr. Strock were not present. Alexander then heard a gunshot. Approaching the sound of the gunshot, Alexander saw that Mr. Strock had been shot and his body had fallen into a gully. Appellant was holding the shotgun. (T.T. p. 1232). Alexander asked appellant why he had shot Mr. Strock. Appellant replied that he was tired of leaving witnesses behind. (T.T. p. 1232). Appellant directed Alexander to go through Mr. Strock’s pockets. (T.T. p. 1234). Alexander complied, handing the items to appellant. Appellant then directed Alexander to shoot Mr. Strock. Alexander *460refused and began walking back to the car when he heard another gunshot. (T.T. p. 1236).
Alexander and appellant got into the Ford Grenada and continued their journey. (T.T. p. 1237). Appellant and Alexander ultimately abandoned Mr. Strock’s Grenada when it ran out of gas. (T.T. p. 1240). Appellant and Alexander continued hitchhiking until they were apprehended in Pottsdam, New York. At the time of the arrest, the officers discovered a .20 gauge sawed-off shotgun. (T.T. p. 1252). While in the custody of the New York police, Alexander agreed to cooperate with authorities and assist them in locating Mr. Strock’s body. In furtherance of this objective, Alexander waived extradition from New York to Pennsylvania and it was agreed that the authorities would bring no charges against him in the State of New York. (T.T. p. 1253). Upon returning to Pennsylvania, Alexander assisted the Pennsylvania State Police in locating the body.
Alexander ultimately testified for the Commonwealth at appellant’s trial. Prior to trial, appellant had requested any evidence pertaining to an agreement between Alexander and the Commonwealth. The assistant district attorneys prosecuting the case assured appellant that no deal had been made in exchange for Alexander’s testimony. Alexander denied that his testimony against appellant was in exchange for favorable treatment by the Commonwealth, although Alexander was also facing trial on charges of murder and kidnapping arising from the same incident.2 (T.T. p. 1303). Subsequent to appellant’s trial, Alexander entered a plea of guilty on the charges of murder and kidnapping in exchange for a sentence of 40 months’ of incarceration. (H.T. p. 33). Appellant was convicted of first-degree murder and sentenced to death on October 30, 1984. The judgment of sentence was affirmed in Commonwealth v. Strong, 522 Pa. 445, 563 A.2d 479 (1989), cert. denied, 494 U.S. 1060, 110 S.Ct. 1536, 108 L.Ed.2d 775 (1990).
*461In 1995 appellant filed a pro se petition seeking post-conviction relief. Counsel was appointed to assist appellant and an amended petition was filed. Evidentiary hearings were held on April 7th and 8th, and May 8th, 1997. On June 30, 1998 the lower court denied the petition for PCRA relief. This direct appeal followed.3
In preparation for the post-conviction evidentiary hearing scheduled for April 7, 1997, appellant’s counsel requested copies of all relevant documents contained in the prosecution’s file. On April 3, 1997, several letters were faxed to counsel which revealed that Alexander’s public defender and the District Attorney of Luzerne County had been discussing an agreement with Alexander prior to appellant’s trial. This was the first time this information was made available to appellant. Appellant alleged at the post-conviction hearing that in failing to reveal this information, which he specifically requested prior to trial, the prosecution had deprived him of a fair trial in accordance with the dictates of Brady. During the course of the evidentiary hearing, testimony was elicited regarding these letters and any possible deal between Alexander and the Commonwealth impacting upon Alexander’s credibility at appellant’s trial. At the conclusion of the testimony, the trial court determined that there was no actual deal struck between Alexander and the Commonwealth; therefore, there was no material evidence that had been withheld from appellant and thus no Brady violation.
Appellant asserts that the trial court erred in its determination that Brady had not been violated. To obtain relief on this claim pursuant to the PCRA, appellant must establish that the constitutional violation at issue so undermined the truth determining process that no reliable adjudication of guilt or innocence could have taken place. 42 Pa.C.S. *462§ 9543(2)(i); see Commonwealth v. Kimball, 555 Pa. 299, 724 A.2d 326 (1999). In assessing appellant’s right to relief, we must determine whether a Brady violation occurred.4
In Brady, the United States Supreme Court declared that due process is offended when the prosecution withholds evidence favorable to the accused. Id. at 87, 83 S.Ct. 1194. Brady and a co-defendant, Boblit, were tried and convicted of first-degree murder in separate trials. Brady was tried first, and testified on his own behalf, naming Boblit as the actual killer. Prior to trial Brady had requested Boblit’s extrajudicial statements. The prosecution turned over several statements, but withheld one statement wherein Boblit admitted that he committed the actual killing. The United States Supreme Court found the action of the prosecutor in withholding Boblit’s statement violative of Brady’s right to due process. The Brady decision extended the principle of Mooney v. Holohan, 294 U.S. 103, 55 S.Ct. 340, 79 L.Ed. 791 (1935), which prohibits the prosecution from obtaining a conviction through deliberate deception. The Brady court established the obligation of the prosecution to respond affirmatively to a request for production of exculpatory evidence with all evidence material to the guilt or punishment of the accused .5 Where evidence material to the guilt or punishment of the accused is withheld, irrespective of the good or bad faith of the prosecutor, a violation of due process has occurred. Brady, at 87, 83 S.Ct. 1194.
Exculpatory evidence favorable to the accused is not confined to evidence that reflects upon the culpability of the defendant. Exculpatory evidence also includes evidence of an impeachment nature that is material to the case against the accused. Napue v. Illinois, 360 U.S. 264, 269, 79 S.Ct. 1173, 3 *463L.Ed.2d 1217 (1959). As the court in Napue sagely observed: “[t]he jury’s estimate of the truthfulness and reliability of a given witness may well be determinative of guilt or innocence, and it is upon such subtle factors as the possible interest of the witness in testifying that a defendant’s life or liberty may depend.” Id. at 269, 79 S.Ct. 1173. Any implication, promise or understanding that the government would extend leniency in exchange for a witness’ testimony is relevant to the witness’ credibility. United States v. Giglio, 405 U.S. 150, 154, 92 S.Ct. 763, 31 L.Ed.2d 104 (1972). As Brady and its progeny dictate, when the failure of the prosecution to produce material evidence raises a reasonable probability that the result of the trial would have been different if the evidence had been produced, due process has been violated and a new trial is warranted. United States v. Bagley, 473 U.S. 667, 105 S.Ct. 3375, 87 L.Ed.2d 481 (1985).
Appellant alleges a Brady violation occurred in this case because despite appellant’s requests, the Commonwealth denied the existence of any arrangement with Alexander relevant to Alexander’s testimony against appellant. The trial court found no violation as the evidence failed to reveal the existence of a completed deal between the Commonwealth and Alexander prior to appellant’s trial. However, Brady does not require a signed contract between the prosecution and its witnesses.
In Giglio, the government needed the testimony of Taliento, a bank teller, in order to convict Giglio in a scheme involving forged money orders. The government attorney who presented the case to the grand jury “promised” Taliento that he would not be prosecuted for his part in the scheme. Taliento testified against Giglio before the grand jury and at trial. Although Taliento was listed on Giglio’s indictment as a co-conspirator, Taliento was not indicted. At trial Taliento did not reveal the promise. A different government attorney tried the case, and in his closing argument stated that no promises had been made regarding Taliento’s testimony. The trial attorney had not been informed of the promise made by *464the attorney who prepared the case before the grand jury. The matter of Taliento’s promise was not discovered until after Giglio had been convicted. The United States Supreme Court found that it was irrelevant which attorney made the promise and that the first attorney failed to reveal the promise to the second attorney, because for Brady purposes, the prosecutor’s office is one entity. Id. at 154, 92 S.Ct. 763. The critical point for the Court in Giglio was that Taliento was a crucial witness and thus, his credibility was an important issue for the jury in resolving Giglio’s culpability. Any evidence of 'an understanding or promise regarding Taliento’s testimony was relevant and the jury was entitled to that knowledge. As Giglio made clear, due process requires that any potential understanding between the prosecution and a witness be revealed to the jury.
In reviewing appellant’s allegation of a Brady violation, we begin with the letters that were turned over four days prior to the evidentiary hearing. (Appellant’s exhibit A). A condensed chronological summary of the four letters is as follows. On December 6, 1983, Alexander’s attorney, Bruce Miller, wrote to the District Attorney of Luzerne County, Robert J. Gillespie, Jr. In that letter, Miller referenced an earlier conversation with Gillespie regarding a deal for Alexander to receive a two year jail term upon a plea to the pending murder charges. Miller wrote that in light of Alexander’s prior record and the sentencing guidelines, the court would probably reject two years. But Miller agreed that three years was appropriate “in view of the cooperation Mr. Alexander has given up to this point and will give to the Commonwealth in the future.” The second letter is dated December 12, 1983, and was written by Robert J. Gillespie, Jr. to John Mauro, the State Police Trooper in charge of the investigation of Mr. Strock’s murder. That letter forwarded the December 6th letter of Mr. Miller and stated “I believe it’s time we sit down and firmly discuss our deal with Alexander so that we can go forward.” The third letter, dated January 26, 1984, is from Attorney Miller to District Attorney Gillespie. In that letter, Miller reported that Alexander had complained of his prison *465situations and he sought accommodation for Alexander, “considering the cooperation that Mr. Alexander is offering to the Commonwealth, it does not appear that this request is unreasonable.” On January 27, 1984, District Attorney Gillespie responded to Miller’s letter with the statement that he had no control over the current placement of Alexander, but that he would forward Miller’s letter to the warden.
After the admission of these letters into evidence, several witnesses were called. James Alexander testified that his trial testimony against appellant was in exchange for a deal for minimum jail time on his pending charges of murder and kidnapping. (H.T.15). Alexander could not recall the names of the attorneys involved, but he did recall being advised to state that no deal had been made when he testified at appellant’s trial. (H.T.15, 28). Alexander acknowledged that he had completed his jail term and parole prior to coming forward at appellant’s evidentiary hearing. (H.T.83).
Appellant’s trial counsel, Michael Kostelansky, testified that he was of the belief that the Commonwealth had procured Alexander’s testimony by striking a deal favorable to Alexander. (H.T.379).6 Kostelansky made several attempts to discover a plea agreement, or any arrangement between *466Alexander and the Commonwealth. The Commonwealth always denied the existence of any arrangement with Alexander. (H.T.380). Kostelansky had never seen the letters referred to herein prior to the evidentiary hearing. (H.T.389). If he had known of the letters, he stated that he would have used them in cross-examining Alexander, as he believed Alexander’s credibility was a critical issue in appellant’s trial. (H.T.426-7).
Anthony Lumbis, co-counsel for appellant at trial, recalled having similar suspicions as those of Attorney Kostelansky regarding a deal between Alexander, and the Commonwealth. (H.T.679). Attorney Lumbis had never seen the letters at issue until the evidentiary hearing. (H.T.682). He testified that had the letters been known they would have been helpful in supporting evidence of a deal regarding Alexander’s testimony. (H.T.703).
Robert J. Gillespie, Jr. testified that he had no recollection of the letters at issue. (H.T.565). However, he did recall discussions with Mr. Miller regarding consideration for Alexander. (H.T.568). Mr. Gillespie was positive that no plea agreement was made, for if one had been arranged it would have been on the record. (H.T.577). Mr. Gillespie elaborated that it was his practice as District Attorney of Luzerne County at the time of appellant’s trial to avoid entering into plea agreements until after receiving the cooperation. (H.T. 577). Rather, it was his “normal course to indicate that truthful cooperation would get consideration.” (H.T.577). Mr. Gillespie acknowledged that Brady concerns factored in to his policy on plea agreements because the jury would have to be apprised of any such agreement. (H.T.578). Mr. Gillespie described the letters at issue as negotiations, not evidence of a deal. (H.T.599). He acknowledged that a fair statement would be that Alexander testified in hopes of getting consideration for himself. (H.T.603).
Attorney Bruce Miller represented Alexander. (H.T.717). Mr. Miller had no recollection of the letters, but upon review he found them indicative of negotiations on behalf of Alexander. (H.T.726). He testified that he would not have told *467Alexander to lie about a deal for his testimony. (H.T.743). Attorney Miller admitted the possibility that he may have advised Alexander to testify in hopes of favorable consideration. (H.T.751-2). Attorney Miller also admitted to the possibility that an unwritten agreement may have existed regarding a deal between Alexander and the Commonwealth. (H.T. 756-7).
John Eichorn and Daniel Pillets, the Assistant District Attorneys who prosecuted appellant, testified to no knowledge of the letters. (H.T.793, 815). Both attorneys denied the existence of any deal with Alexander. (H.T.782, 805). Both attorneys testified that if they had known of the letters, Brady would require their disclosure. (H.T.795, 814).
We agree with the trial court’s finding that the witnesses were credible in stating that there was no deal struck, and that there was no definitive agreement between Alexander and the prosecution. In addition, we concur in the trial court’s assessment that Alexander’s testimony as to the existence of an agreement lacked credibility. Alexander could not recall the name of his attorney, or of the District Attorney who negotiated an agreement on his behalf, nor could he recall the particulars of the deal. However, we note that the absence of an ironclad contract in exchange for Alexander’s testimony is not dispositive. See Giglio, supra. Therefore, we do not agree with the trial court’s assessment that these factors are determinative of appellant’s Brady claim.
Even if we disregard Alexander’s testimony at the evidentiary hearing, sufficient circumstantial evidence of an understanding between Alexander and the Commonwealth regarding Alexander’s testimony at appellant’s trial exists. Alexander and appellant had each been indicted on charges of murder, kidnapping and conspiracy. The Commonwealth did not seek a joint trial of the alleged coconspirators, and in fact dropped the conspiracy charge against Alexander prior to appellant’s trial. The Commonwealth, as the letters revealed, had offered Alexander a sentence of two years on the charges of murder and kidnapping, pending information on his prior *468record. Mr. Miller, upon receipt of the prior record information, indicated a willingness to have Alexander plead guilty in exchange for a sentence of 36 months, rather than -24 months. Ultimately, Alexander pled guilty and received a sentence of 40 months. Unlike the trial court, we do not find this additional 4 months to be a critical departure from the understanding that the parties had been discussing prior to appellant’s trial. The fact that the trial prosecutor was unaware of the negotiations between his superior and counsel for Alexander is irrelevant. As the United States Supreme Court has repeated time and again, the good faith or the bad faith of the individual prosecutor is irrelevant in determining whether or not the accused has been afforded a fair trial. Giglio, 405 U.S. at 154, 92 S.Ct. 763. Accordingly, we find the record establishes the existence of an understanding between the Commonwealth and Alexander that he would be treated with considerable leniency in exchange for his testimony against appellant. This understanding although not articulated in an ironclad agreement, was sufficient to implicate the due process protections of Brady.
Having found that an understanding existed between Alexander and the Commonwealth, which was sufficient to trigger Brady, we must next determine if that understanding was material, thus entitling appellant to relief. As stated previously, impeachment evidence is material, and thus subject to obligatory disclosure, if there is a reasonable probability that had it been disclosed the outcome of the proceedings would have been different. Bagley, 473 U.S. at 678, 105 S.Ct. 3375; Agurs, 427 U.S. at 112-113, 96 S.Ct. 2392; Commonwealth v. Wallace, 500 Pa. 270, 455 A.2d 1187, 1192 (1983).
The evidence at appellant’s trial established that appellant and Alexander were hitchhiking together. Several witnesses were called who gave rides to the two men. Appellant was seen with Alexander in the victim’s car. Appellant and Alexander had in their possession the identification of the victim and certain of his belongings at the time of their arrest. In appellant’s luggage, police recovered a .20 gauge sawed off shotgun. Alexander had in his possession a bloodstained *469handkerchief. (T.T. 1667). The blood was Type A, the same blood type as Alexander and as Mr. Strock. (T.T. 1678). Testimony of a firearm expert established that the shot pattern of the shotgun recovered at the time of arrest was similar to the shot pattern of the weapon that was used on the victim. (T.T. 1663). The expert conceded that there would be no way to exactly identify the shotgun used to kill Mr. Strock. (T.T. 1664).
This circumstantial evidence places Alexander and the appellant in exactly the same position regarding their culpability for the death of John Strock. The crucial fact that alters this equation is Alexander’s testimony. During trial, appellant testified that he was hitchhiking with Alexander from Pennsylvania to New York. (T.T. 1717). Appellant testified that Alexander was the person who brought along the shotgun. (T.T. 1721). However, at some point in their progress along the highways they separated, as it was difficult for two men to get rides together. (T.T. 1735). A day or so later they happened upon each other at a rest stop at which time Alexander had in his possession the items later identified as belonging to the victim. (T.T. 1750).
There are obvious discrepancies between appellant’s and Alexander’s testimony. Given that James Alexander is the key witness who puts the gun in appellant’s hand at the moment of the murder, his credibility was decisive to the jury’s finding as to appellant’s guilt. Impeachment evidence which goes to the credibility of a primary witness against the accused is critical evidence and it is material to the case whether that evidence is merely a promise or an understanding between the prosecution and the witness. The absence of an ironclad, signed, sealed contract does not conclusively establish that no other information affecting the credibility of the witness exists. Giglio, at 155, 92 S.Ct. 763. To the contrary, the fact that there was no binding agreement regarding Alexander’s deal in exchange for his testimony, but rather only a contingency dependent upon the Commonwealth’s satisfaction with the end result, only strengthens Alexander’s motive to testify favorably for the Commonwealth. *470Bagley, 473 U.S. at 683, 105 S.Ct. 3375.7 The facts in this case strongly indicate that Alexander’s testimony was in exchange for what he believed would be a beneficial outcome to him. That understanding was material information that appellant’s jury should have been informed of when weighing Alexander’s credibility. There is a reasonable probability that had this information been revealed, the outcome of appellant’s trial would have been different. Bagley, supra., Agurs, supra., Giglio, supra., Brady, supra.
Appellant has established a due process violation as the Commonwealth failed to disclose exculpatory information concerning .the credibility of its key witness. The Commonwealth’s failure to comply with Brady is a violation of the Fourteenth Amendment of the United States Constitution. As demonstrated above, that violation undermined the truth-determining process so that no reliable adjudication of appellant’s guilt or innocence could have taken place. Kimball, supra., Wallace, supra. Thus, appellant has met the criteria for relief under the PCRA. 42 Pa.C.S. § 9543(2)(i).
Accordingly, this matter is remanded for a new trial.
Jurisdiction is relinquished.
Justice CASTILLE files a concurring opinion joined by Justice NEWMAN.. As we find the Brady issue dispositive we do not review appellant’s other claims of error.
. The Commonwealth dropped the charge of conspiracy against Alexander prior to appellant’s trial. Post Conviction Hearing Transcript (hereinafter "H.T.” p. 378).
. In proceedings under the PCRA, the scope of review of an appellate court is limited by the parameters of the act. 42 Pa.C.S. § 9541 et seq. Since most PCRA appeals involve, as in this case, issues raising mixed questions of fact and law, our standard of review is whether the findings of the PCRA court are supported by the record and free of legal error. See Commonwealth v. Allen, 557 Pa. 135, 732 A.2d 582, 586 (1999); 42 Pa.C.S. § 9543.
. Whether or not a Brady violation occurred must be determined in accordance with the status of the law at the time of appellant’s trial in 1984.
. The rule of Brady has been extended to require the prosecution to disclose exculpatory information material to the guilt or punishment of an accused even in the absence of a specific request. United States v. Agurs, 427 U.S. 97, 96 S.Ct. 2392, 49 L.Ed.2d 342 (1976); Commonwealth v. Moose, 529 Pa. 218, 602 A.2d 1265 (1992).
. Kostelansky testified to receiving a phone call, at the time of appellant's trial, from a confidential source telling him that a deal existed between Alexander and the Commonwealth. (H.T.382). On the strength of this tip, without revealing the source, he renewed the Brady request for information about a plea arrangement between Alexander and the Commonwealth. The Commonwealth again denied the existence of any deal. At the evidentiary hearing, the trial court directed Kostelansky to reveal the source of the tip. (H.T.383). Kostelansky named Russell Thomas, an investigator for the Office of the Public Defender of Luzerne County. At the time of appellant’s trial, a defense request for appointment of a private investigator was denied, and Mr. Thomas was directed to work as the investigator for appellant, while he was also the investigator for the Public Defender. (H.T.435). The Public Defender represented Alexander. Mr. Thomas testified that he had no recollection of making a call to Kostelansky regarding a deal with Alexander. (H.T.438). At the time of the evidentiary hearing, Thomas was still employed as an investigator for the Public Defender of Luzerne County. In a related argument, appellant alleges that Thomas' simultaneous functioning as investigator for him and Alexander created a conflict of interest detrimental to appellant’s case. Given our resolution of this matter we do not address this issue.
. Only Justice O’Connor joined this portion of Justice Blackmun’s opinion.