This case is before this court on certification from the court of appeals to review an order of the Circuit Court for Racine County, HON. RICHARD G. HARVEY, JR., presiding. The defendant-appellant, Alan Rivest, appeals from an order granting the state’s motion to vacate a plea agreement entered on February 6,1979.
On the afternoon of June 5, 1978, Floyd Jensen was murdered and robbed in his gasoline service station in Caledonia, Wisconsin. Shortly after the murder-robbery, *408Alan Rivest surrendered to police. Rivest, in a statement given to the police, admitted participating in the robbery of the gas station owner, but denied any involvement in his subsequent murder. Rivest indicated in his statement that Edward Rodriguez, his accomplice, repeatedly stabbed Jensen during the robbery and that he did not participate therein and that he fled the gas station before Rodriguez but after the stabbing.
Later that same evening on June 5,1978, Rivest signed a sworn statement dictated to the police in which he repeated his earlier statement and denied any involvement in the stabbing of Floyd Jensen.
Rivest, a minor, was initially charged with delinquency for the murder and armed robbery of Floyd Jensen in the juvenile court and was subsequently waived into adult court on August 1, 1978. After his waiver into adult court, Rivest was not charged with being a party to first-degree murder. Thomas Finley, the assistant district attorney handling the case, agreed with Rivest and his attorney that the state would withhold the murder charge pending the completion of a final plea agreement. Based upon Rivest’s prior statements and his investigation, Assistant District Attorney Finley charged Rivest only with the crime of armed robbery on August 3,1978.
On September 25, 1978, Rivest took a private polygraph examination which indicated that he was truthful in his denial of any participation in the stabbing of Floyd Jensen. The results of the polygraph examination were presented to the assistant district attorney. Subsequent negotiations between Rivest, his attorney and the Assistant District Attorney Finley produced a plea agreement. In the plea agreement, Rivest agreed to (1) plead guilty to a charge of robbery; (2) testify against Rodriguez whenever requested; and (3) pass a second polygraph examination conducted by a party chosen by the district *409attorney. On January 24, 1979, Rivest took the second polygraph examination conducted by the police and the test indicated that Rivest was unaware that an assault was to be perpetrated on Jensen, and did not participate in stabbing Jensen.
At a hearing on February 6, 1979, the plea agreement entered into between Rivest and the assistant district attorney was placed on the record and Rivest pled guilty to the crime of robbery, reduced from armed robbery, and was convicted on that plea. Rivest was sentenced to six years in prison and is presently serving that sentence.
On February 19, 1979, Rivest testified at the preliminary hearing of Edward Rodriguez. At the hearing, Rivest testified that he never got near Jensen nor did he come in physical contact with him. He also testified that he ran “straight out across the street” shortly after Rodriguez stabbed Jensen.
Subsequent to Rivest’s testimony at the preliminary hearing, the district attorney, Dennis Barry, while preparing the Rodriguez murder file, reviewed evidence which he believed directly contradicted both Rivest’s initial statements to the police and his testimony at the preliminary hearing. This evidence established that there was a three to five minute delay between the time Jensen’s body was discovered and the time that witnesses saw Rivest and Rodriguez flee the scene together. The evidence also proved that a “herringbone pattern” on the forehead of the victim matched the “herringbone pattern” on Rivest’s shoes, but not Rodriguez’ shoes. Finally, a State Crime Lab report indicated that the large bloodstains present on Rivest’s pants and uhdershorts matched the blood type and factors of Floyd Jensen.
Based upon this evidence, District Attorney Barry interviewed Rivest and confronted him with this evidence. At that interview, Rivest admitted leaving the gas station by a different door than the one he had *410originally testified he exited from. However, Rivest offered no explanations for the presence of his shoe print on the deceased’s head nor the presence of the deceased’s blood on his clothing and he continued to reiterate his former account of the stabbing.
District Attorney Barry concluded after the interview that Rivest’s account of the circumstances surrounding the stabbing were untrue, and that his prior and continued statements and testimony were false and thus, he breached the plea agreement. Based upon this evidence, District Attorney Barry decided not to present Rivest’s testimony at the Rodriguez trial.
Thereafter, on August 21, 1979, the state filed first-degree murder charges against Rivest. The same day, the defendant secured a writ of habeas corpus from Circuit Judge John C. Ahlgrimm to bar prosecution of the first-degree murder charge. After holding extensive hearings on the matter, Judge Ahlgrimm ruled that before the murder charge could be prosecuted, the state would have to secure an order vacating the plea agreement from the judge who originally approved the plea agreement.
The state then filed a motion before Judge Harvey to vacate and set aside the plea agreement and guilty plea. After hearings and arguments, Judge Harvey entered an order setting aside the plea agreement and guilty plea and authorized the state to continue the prosecution of the murder complaint. The court held that Rivest had fraudulently induced the state to enter into the plea agreement through his false and misleading statements and had materially breached the agreement by giving false testimony at Rodriguez’ preliminary hearing.
The court of appeals granted a permissive appeal from this order, pursuant to sec. 809.50, Stats., and petitioned this court for certification.
*411 Issues
1. Did Rivest materially breach the plea agreement entered on February 5, 1979, by giving false testimony at Rodriguez’ preliminary hearing?
2. Did Rivest fraudulently induce the state to enter into the plea agreement?
Breach of Plea Agreement
This case raises issues concerning both the standard for setting aside a plea agreement and the procedure to be employed where the state seeks to vacate a plea agreement after a defendant has commenced serving the sentence imposed. These are questions of first impression in Wisconsin, although decisions of several other jurisdictions have established procedures and standards for vacating plea agreements previously approved by a court.
The Supreme Court of Nevada in the decision of Gamble v. State, 604 P.2d 335 (Nev. 1979), summarized the procedure applicable when the state seeks to be released from its obligations under a plea bargain:
“. . . [W]hen the prosecution contends that it should be released from its obligations under a plea bargain because of an alleged breach of the agreement by the defendant, an evidentiary hearing is required to determine whether the defendant actually breached the agreement, and, if so, whether the breach is sufficiently material to warrant releasing the prosecution from its promises. United States v. Donahey, 529 F.2d 831 (5th Cir. 1976) ; see also United States v. Nathan, 476 F.2d 456 (2d Cir. 1973).” Id. at 337.
The rationale underlying this requirement of an evidentiary hearing concerning the alleged breach of a plea agreement has been summarized in the following manner:
“On the merits, our view is that in a plea bargain the government’s obligation to make a recommendation *412arises only if defendant performs his obligation (in this instance, full disclosure), but the question whether defendant did in fact fail to perform the condition precedent is an issue not to be finally determined unilaterally by the government, but only on the basis of adequate evidence by the Court which, in accordance with Santobello v. New York, 404 U.S. 257, 92 S. Ct. 495, 30 L. Ed 2d 427 (1971), judicially approved the bargain as meeting governing standards. There would be manifest impropriety in permitting the government, without satisfying a judge that the evidence proves that a defendant broke his promise, to escape from the obligation the government undertook in the plea bargain.” United States v. Simmons, 537 F.2d 1260 (4th Cir. 1976). (Emphasis supplied.)
In the case at bar, several days of hearings were held to establish both the terms of the plea agreement entered into by Alan Rivest and the breach of that agreement before Judge Ahlgrimm in the habeas corpus action. By stipulation of the parties, the transcript of these proceedings and the evidence presented therein were used as the basis for Judge Harvey’s decision of the state’s motion to vacate the plea agreement.1 Based upon this testimony and evidence, Judge Harvey, who had initially approved the plea agreement, held that the evidence established beyond a reasonable doubt that Rivest had fraudulently induced the plea agreement and had breached its terms. Thus, we hold that the extensive proceedings before Judge Harvey satisfied the procedural requirement of an evidentiary hearing establishing the grounds for vacating a plea agreement.
We next address the question of the appropriate standard to be applied in determining whether a plea agree*413ment has been breached by a defendant. Other courts which have addressed this question have relied on contract law analogies in determining questions of the validity of a plea agreement:
“Courts have frequently looked to contract law analogies in determining the rights of defendants aggrieved in the plea negotiation process. See Cooper v. United States, 594 F.2d 12, 15-16 (4th Cir. 1979); Westen & Westin, A Constitutional Law of Remedies for Broken Plea Bargains, 66 Cal. L. Rev. 471, 530 (1978). It is clear that a defendant’s failure to fulfill the terms of a pretrial agreement relieves the government of its reciprocal obligations under the agreement. United States v. Simmons, 537 F.2d 1260, 1261 (4th Cir. 1976); United States v. Resnick, 483 F.2d 354, 358 (5th Cir.), cert. denied, 414 U.S. 1008, 94 S. Ct. 370, 38 L. Ed. 2d 246 (1973) ; United States v. Nathan, 476 F.2d 456, 459 (2d Cir.), cert. denied, 414 U.S. 823, 94 S. Ct. 171, 38 L. Ed. 2d 56 (1973).” United States v. Calabrese, 645 F.2d 1379, 1390 (10th Cir. 1981).
While analogies to contract law are important to the determination of questions regarding the effects of a plea bargain, such analogies are not solely determinative of the question as fundamental due process rights are implicated by the plea agreement.
“The analogy to contract law doctrines is not determinative in the area of plea negotiation, however. Because important due process rights are involved, plea negotiations must accord a defendant requisite fairness and be attended by adequate ‘safeguards to insure the defendant what is reasonable [in] the circumstances.’ Santobello v. New York, 404 U.S. 257, 262, 92 S. Ct. 495, 498, 30 L. Ed. 2d 427 (1971); see Cooper v. United States, 594 F.2d 12, 15-20 (4th Cir. 1979).” Id. at 1390.
This is consistent with this court’s prior recognition that cases concerning the enforcement of plea agreements require the application of the doctrine of due process.
*414“While none of the cases enforcing- the district attorney’s agreement approach the issue in terms of due process of law, we consider the facts constituting good public policy require the application of the doctrine of due process, which rests upon ‘that whole community sense of “decency and fairness” that has been woven by common experience into the fabric of acceptable conduct.’ Breithaupt v. Abram (1957), 352 U.S. 432, 436, 77 Sup. Ct. 408, 1 L. Ed 2d 448.” Austin v. State, 49 Wis. 2d 727, 736, 183 N.W. 2d 56 (1971).
By analogy to contract law, we conclude that a plea agreement may be vacated where a material and substantial breach of the plea agreement has been proved. To allow a defendant to claim the benefit of an agreement where he, himself, is in default, offends fundamental concepts of honesty, fair play and justice.
We further hold that the constitutional due process requirements of “decency and fairness” are satisfied where the burden is placed upon the party seeking to vacate the agreement to establish both the breach, and that the breach is sufficiently material to warrant releasing the party from its promises (prosecution or defense) before the same judge who accepted the plea, whenever possible.
Our holding that a prosecutor is relieved from the terms of a plea agreement where it is judicially determined that the defendant has materially breached the conditions of the agreement is consistent with numerous decisions in other jurisdictions holding that a party is not bound to a plea agreement where the other party is in substantial default of a material issue. See: United States v. Calabrese, 645 F.2d 1379 (10th Cir. 1981); United States v. Nathan, 476 F.2d 456 (2d Cir. 1973) ; United States v. Simmons, 537 F.2d 1260 (4th Cir. 1976); United States v. Donahey, 529 F.2d 831 (5th Cir. *4151976); Adamson v. Superior Court of Arizona, 125 Ariz. 579, 611 P.2d 982 (Ariz. 1980); Gamble v. State, 604 P.2d 335 (Nev. 1979); People v. Clark, 72 Mich. App. 752, 250 N.W.2d 774 (Mich. Ct. App. 1977).
The trial court, in its decision on the motion to set aside the plea bargain, found that Alan Rivest testified falsely that he had no physical contact with Floyd Jensen as demonstrated in the following excerpt from Ri-vest’s testimony at the preliminary hearing:
“Q. Did you ever get near Mr. Jensen ? A. No.
“Q. So I guess you don’t know if there was blood found on your underwear or not ? A. No.
“Q. So you don’t know if there was any how [sic] it would have gotten there? A. Right.
“Q. Did you at any time have any physical contact with Mr. Jensen on that date? A. No, sir.”
The judge in his ruling setting aside the plea agreement and guilty plea referred to the medical testimony establishing the presence of blood of a type matching that of Jensen on Rivest’s clothing and Rivest’s shoe print on Jensen’s head in support of these conclusions. The court further found that Rivest had testified falsely concerning both the time and manner in which he fled the gas station. Rivest did not explain the apparent falsity of his statement concerning his exit, physical contact with Jensen and bloodstains on his clothing when interrogated by District Attorney Barry nor has he offered an explanation to date. Finally, the court in its supplemental findings expressly held that one of the conditions of the plea agreement was that Rivest would give truthful testimony at the preliminary hearings and all other proceedings. These were findings of fact made by the trial court and as such they must be upheld by an appellate court unless they are clearly erroneous and against the great weight *416and clear preponderance of the evidence. Aetna Life Ins. Co. v. Mitchell, 101 Wis. 2d 90, 110, 303 N.W.2d 639 (1981).
The conclusion that the trial court’s findings are not erroneous nor against the great weight of the evidence is established by the clear, convincing and unrebutted scientific testimony and physical evidence of Jensen’s blood on Rivest’s clothing, Rivest’s shoe print on Jensen’s head and the testimony concerning Rivest’s delayed departure from the gas station. The testimony of both Rivest’s attorney and the prosecutor at the habeas corpus proceeding demonstrates that it was implicit in the plea agreement that Rivest’s testimony was to be truthful and thus we agree that the trial court’s finding on that issue is supported by the evidence.
The evidence at the hearings in the habeas corpus action established that Rivest in all probability played a significantly greater role in the murder of Floyd Jensen than he owned up to or testified to and that evidence compels us to hold that Rivest’s perjured testimony materially breached the plea agreement. Rivest’s attempts to completely exculpate himself from involvement in the stabbing death of Floyd Jensen, through false testimony, deprived the state of a material and credible witness for use in the prosecution of Rodriguez and, therefore, prevented the state from receiving the benefit it sought when consenting to the plea agreement. Thus, we hold that the trial court was correct in vacating the plea agreement and guilty plea based upon Rivest’s material breach.
Rivest argues that his inconsistent testimony was not a sufficient breach of the plea agreement to justify the vacation of the agreement. We disagree with this contention. It is ludicrous for the defendant to argue that his perjurous testimony was anything less than a grave and material breach of the plea agreement. It is funda*417mental to the American system of jurisprudence that a witness testify truthfully. Without truthful testimony, it is nigh onto impossible to achieve the primary goal of our judicial system, justice. It is because the search for the truth is central to our legal proceedings that we require each witness to take an oath of truthfulness prior to testifying. Thus, to say that the giving of false testimony of a material fact is not a material breach of a promise to testify truthfully is to undermine and corrupt the very basic premise upon which our judicial system was founded and operates to date.
The legislature has sought to reinforce the importance of truthful testimony by making the breach of the wit-hess’ oath of truthfulness as to a material fact a felony. Similarly, the ethical rules governing all attorneys forbid the knowing acquiescence in false testimony and in this case required that neither the prosecutor nor defense counsel present Rivest’s false testimony which was so false and unbelievable as to be useless in prosecuting Rodriguez. The falsity of Rivest’s testimony, if knowingly used at trial, would have rendered the conduct of the attorney presenting the testimony unethical and illegal.
We note that other courts have found similar instances of incredible testimony sufficient to void plea agreements. In United States v. Eucker, 532 F.2d 249 (2d Cir. 1976), the court held that the prosecutor was not bound by a plea agreement where the defendant gave completely exculpatory testimony after agreeing to cooperate in the prosecution of a co-defendant.
“The Assistant United States Attorney who represented the Government on the trial promised Sloan that if he pleaded guilty and cooperated in the preparation and presentation of the case against Anderson, the Government would ‘go to bat’ for him. Thereafter, Sloan pleaded guilty. However, his cooperation consisted of presenting the prosecution with a version of the facts in *418which he attempted to completely exculpate himself from any wrongdoing-. Under these circumstances the Government was unwilling to vouch for his credibility and did not call him as a witness. The prosecutor also did not ‘go to bat’ for him, because he did not consider Sloan’s willingness to testify falsely to be cooperation.” Id. at 256.
Similarly, in the case at bar, Rivest, through his testimony at the preliminary hearing, sought again to completely exculpate himself from any involvement in the stabbing of Jensen in spite of the scientific and physical evidence possessed by the prosecution which directly conflicted with Rivest’s testimony. As in the case of United States v. Eucker, supra, and the case at bar, it was proper for District Attorney Barry not to use Rivest’s testimony in the trial of his accomplice, and to consider the plea agreement breached.
In United States v. Donahey, supra, the court relieved the prosecution of the terms of a plea agreement where the defendant gave “evasive and misleading answers,” and answers “which could not be verified after agreeing to fully co-operate in the prosecution of co-defendants.” Id. at 832. Likewise, Rivest’s testimony at Rodriguez’ preliminary examination was evasive and misleading and to date has not been explained by Rivest.
Rivest finally argues that an alleged delay in seeking a vacation of the plea agreement in the present case violated his constitutional right to due process and requires the reinstatement of the plea agreement. Where a defendant seeks to avoid prosecution based upon prosecu-torial delay, it is clear that it must be shown that the defendant has suffered actual prejudice arising from the delay and that the delay arose from an improper motive or purpose such as to gain a tactical advantage over the accused.
*419“In Lovasco, 431 U.S. at 789, the United States Supreme Court stated that the due process clause ‘has a limited role to play in protecting against oppressive delay.’ However, it rejected the defendant’s argument that due process precludes prosecution whenever a defendant suffers actual prejudice arising out of preindictment delay. The court explained that actual prejudice may make a due process claim ‘concrete and ripe for adjudication,’ and is a necessary element of such a claim. 431 U.S. at 789-790. Nonetheless, it continued, a defendant must also prove that the government’s delay in charging arose from an improper motive or purpose such as to gain an unfair ‘“tactical advantage over the accused.’” Quoting United States v. Marion, 404 U.S. 307, 324 (1971).) 431 U.S. at 795.” State v. Davis, 95 Wis. 2d 55, 58, 288 N.W. 2d 870 (Ct. App. 1980).
Referring to the question of prosecutorial delay, we hold that the tests of “actual prejudice” and “improper motive” as set forth in State v. Davis, supra, are applicable to the case at bar.
Rivest was charged with first-degree murder shortly after the beginning of the Rodriguez trial when it became apparent that he had no interest in changing his prior testimony in order to fulfill the plea bargain by truthfully testifying against Rodriguez. This charge was brought only three months after Rivest was confronted by the district attorney with his false testimony and offered an opportunity to explain his earlier account of the stabbing, which he has not done to date. At the time that the murder charge was issued, Rivest was advised and put on notice that the state no longer believed it was bound by the plea agreement. Any subsequent delay is attributable to both the fact that the defendant challenged the issuance of the first-degree murder complaint and the fact that there was no Wisconsin law clearly outlining the proper procedure to be employed when the state seeks to be relieved of the obligation of a plea *420agreement. The alleged delay, therefore, was attributable to procedures, including this appeal, instigated to protect Rivest’s due process rights under the plea agreement. Thus, based upon these facts, we hold that there was no unreasonable delay in the state’s attempt to avoid the plea agreement, nor does the record demonstrate that the delay was due to any improper motive on the part of the district attorney.
Because we hold that the plea agreement and guilty plea were properly vacated due to the breach of that agreement by the defendant, Alan Rivest, it is not necessary to address the question of whether Rivest fraudulently induced the state to enter into the agreement.
Likewise, we do not deal with the question of the time Rivest has spent in incarceration under the sentence imposed on his earlier guilty plea because the fact that Rivest was committed to incarceration is of no consequence in determining whether the plea bargain or guilty plea should be set aside.
By the Cowrt. — The order of the trial court is affirmed.
Because the transcript of the prior hearing was used on stipulation of both parties, we hold that neither can complain that the hearings held before Judge Harvey do not satisfy the requirement of an evidentiary hearing.