delivered the opinion of the court:
The defendant, Enricho Navarroli, was charged on September 21, 1982, in the circuit court of Peoria County in an indictment of two counts with unlawful possession of cocaine with intent to deliver (a Class X offense) and with unlawful possession of cocaine (a Class 1 offense). There were plea negotiations between the defendant and the State’s Attorney, and on August 27, 1984, the defendant moved to compel the State to carry out a claimed plea agreement. He stated that under the terms of the plea agreement, he acted as an informant in various drug investigations in exchange for the State’s promise to reduce the charges against him and to agree to his being given probation plus a fine. The defendant alleged that after he assisted law enforcement officials the State’s Attorney refused to reduce the charges against him. The State denied both the existence of an agreement and the claimed terms.
At a hearing on the motion, the trial court found that there had been the plea agreement the defendant claimed and it ordered “specific performance” of the agreement. The appellate court reversed (146 Ill. App. 3d 466), and we granted the defendant leave to appeal.
The evidence presented at the hearing on the defendant’s motion as to whether there had been a plea agreement was sharply divided. At the conclusion of the hearing, the circuit court stated that the evidence was so conflicting that a fact finder could decide in favor of or against the motion without finding contrary to the manifest weight of the evidence. The court concluded, how*520ever, that an agreement was made and that the defendant fully performed his portion of it. Discussing the terms of the agreement, the circuit court stated:
“Whether or not the prosecution made a specific promise the defendant said it did, the reasonable inference is that the defendant believed so, and that such belief was not unreasonable under these circumstances. To preserve the sanctity of justice, the defendant must prevail. The defendant is entitled to receive probation and a fine. The reduction of the charge, the length and terms of the probation whether or not accompanied by incarceration and the amount of the fine are left to the parties and to the sentencing judge, should the defendant, in fact, plead guilty.”
The appellate court, in reversing, held that even if the plea agreement did exist, the defendant was not entitled to specific performance of the agreement, because he was not deprived of his liberty or any other constitutionally protected interest in reliance on the agreement. The appellate court also judged that the circuit court improperly employed a subjective, rather than objective, test to determine the terms of the agreement. Because of this error, the appellate court did not consider whether the circuit court’s conclusion that a plea agreement existed was contrary to the manifest weight of the evidence.
On appeal, the defendant argues that the circuit court’s conclusion that a plea agreement existed was supported by the preponderance of evidence. He also argues that the appellate court erroneously concluded that the circuit court employed a subjective, rather than an objective, standard in resolving the conflicting testimony. The defendant claims that the circuit court’s references to defendant’s reasonable belief in the agreement and its terms did not make the.court’s conclusions, ones reached on a subjective standard.
*521The defendant contends too that the appellate court erred in concluding that he was not entitled to specific performance of the proposed plea agreement because he was not deprived of any constitutionally protected interest." He asserts that he surrendered constitutional rights guaranteed by the first, fourth, fifth and sixth amendments in reliance upon the State’s agreement to reduce the charge and recommend probation in exchange for his cooperation.
Finally, the defendant submits that the appellate court misused Rule 352, which authorizes a court to dispose of an appeal without oral argument if no substantial question is presented. The defendant says a substantial question was raised in his appeal which required more than a year for the court to decide and which resulted in a split opinion.
The State argues that even if there was a plea agreement, the defendant was not deprived of any constitutional right by virtue of the State’s refusal to comply with the agreement. The defendant is at liberty to proceed to trial. The appellate court, the State says, correctly held that the defendant was not entitled to specific performance of the claimed plea bargain, and the State finally argues that the trial court incorrectly applied a subjective test determining whether there was a plea agreement.
A plea agreement results when the prosecutor and the defendant exchange promises to perform or refrain from performing specified actions. (People v. Davis (1981), 94 Ill. App. 3d 809.) The existence of a plea agreement and its terms and conditions are questions of fact which the trier of fact must determine after assessing the credibility of witnesses and the weight to be given their testimony. (People v. Starks (1986), 146 Ill. App. 3d 843.) If disputed, the terms of the agreement are to be judged under objective standards (People v. *522 Boyt (1984), 129 Ill. App. 3d 1, aff’d (1985), 109 Ill. 2d 403; People v. Davis (1981), 94 Ill. App. 3d 809; United States v. Quan (9th Cir. 1986), 789 F.2d 711), and the court’s determination whether there was a plea agreement should not be reversed unless contrary to the manifest weight of the evidence. It will not be necessary for us to consider whether, as the State contends, the circuit court’s finding that there was a plea agreement, as the defendant claimed, was contrary to the manifest weight of the evidence, nor need we decide whether, in making that finding, the court erroneously employed a subjective, rather than an objective, test. Even assuming, arguendo, that the circuit court correctly found that an agreement existed with terms as the defendant alleges, we must conclude that the prosecutor’s denial of an agreement and refusal to carry out the claimed bargain did not deprive the defendant of due process, and that therefore, the defendant was not entitled to have the assumed agreement enforced.
The enforceability of plea agreements was recognized in Santobello v. New York (1971), 404 U.S. 257, 30 L. Ed. 2d 427, 92 S. Ct. 495, where the Supreme Court held that a defendant who enters a guilty plea in reliance upon the promise of the prosecutor is entitled to a remedy when the prosecutor breaches that promise. The Court cautioned that, “[wjhen a plea rests in any significant degree on a promise or agreement of the prosecutor, so that it can be said to be part of the inducement or consideration, such promise must be fulfilled.” 404 U.S. at 262, 30 L. Ed. 2d at 433, 92 S. Ct. at 499.
In Santobello, however, the prosecutor breached the plea agreement after the defendant entered a plea of guilty. In Mabry v. Johnson (1984), 467 U.S. 504, 81 L. Ed. 2d 437, 104 S. Ct. 2543, the Supreme Court determined that the same constitutional concerns are not implicated when the prosecutor takes a course of action in*523consistent with an alleged plea agreement before the defendant enters a guilty plea. In Mabry, the prosecutor proposed a plea bargain but then withdrew the offer after the defendant’s acceptance and proposed a second, less favorable, plea agreement. The Supreme Court rejected the defendant’s claim that his acceptance of the first plea bargain created a constitutional right to have that bargain specifically enforced. Relying on due process principles, the Mabry Court defined the scope of the constitutional protection afforded a defendant who enters a plea agreement, stating:
“[A] plea bargain standing alone is without constitutional significance; in itself it is a mere executory agreement which, until embodied in the judgment of a court, does not deprive an accused of liberty or any other constitutionally protected interest. It is the ensuing guilty plea that implicates the Constitution. Only after respondent pleaded guilty was he convicted, and it is that conviction which gave rise to the deprivation of respondent’s liberty at issue here.” (Emphasis added.) (467 U.S. at 507-08, 81 L. Ed. 2d at 442,104 S. Ct. at 2546.)
The Court concluded that the defendant’s guilty plea was not involuntary or induced by the withdrawn plea bargain because the defendant knew that the second agreement controlled when he pleaded guilty. Consequently, the Court held that the defendant could not challenge his plea under the due process clause because the claimed breach of the plea bargain did not deprive him of his liberty in any fundamentally unfair manner.
The Supreme Court in Mabry made it clear that due process principles govern the enforceability of plea agreements. (United States v. Coon (8th Cir. 1986), 805 F.2d 822, 824.) Therefore, the controlling issue here is whether the State’s repudiation of the asserted plea agreement constituted a denial of due process, which can be remedied only by allowing the defendant specific en*524forcement of the agreement. This court recently denied enforcement of a plea agreement in a case involving circumstances resembling those here. (People v. Boyt (1985), 109 Ill. 2d 403.) Our holding there governs the disposition of this appeal. In Boyt, the defendant agreed to testify against her codefendant in exchange for the State’s promise to reduce the charge against her. Before the defendant could testify, however, the codefendant pleaded guilty. When the State thereafter refused to reduce the charges, the defendant sought to enforce the bargain. .This court held that, even if there had been an agreement, the defendant did not have a constitutional right under the due process clause to have the agreement enforced. The court reasoned that the State’s repudiation of the agreement did not deprive the defendant of liberty or any other constitutionally protected interest because the defendant did not plead guilty in reliance on the agreement.
Here, as in Boyt, the defendant has not entered a plea of guilty in reliance on the proposed plea agreement. He cannot say he was deprived of liberty by virtue of the State’s refusal to abide by the terms of the claimed plea agreement. The defendant still has the option of pleading not guilty and proceeding to trial.
The defendant asserts that Boyt does not control under the circumstances because he, unlike Boyt, surrendered constitutional rights in reliance on the agreement. Specifically, the defendant argues that he relinquished rights under the first, fourth, fifth and sixth amendments in reliance on the alleged agreement.
The defendant first claims that he surrendered his first amendment right to freedom of association when he was placed among dangerous men at the decision of State officials. He cites no authority to support this contention, nor does our research disclose any. The contention is close to frivolous.
*525The defendant also asserts that he surrendered his rights under the fourth amendment in reliance on the alleged plea bargain. But in this, too, he fails to point out any evidence or authority in support of this claim. He merely says that his “fourth amendment right to be free from search absent a warrant or probable cause arising in exigent circumstances was vanquished by the police policy of searching a confidential informant before and after each such directed association with suspected drug offenders.” Constitutional questions cannot be raised by unsupported and conclusory allegations that a constitutionally protected right has been invaded. (Janson v. Pollution Control Board (1979), 69 Ill. App. 3d 324.) One must state in complete detail from the record how constitutional rights were infringed before a court will consider the constitutional objection. (See People v. Hanserd (1985), 136 Ill. App. 3d 928; Consultants & Administrators, Inc. v. Department of Insurance (1982), 103 Ill. App. 3d 920.) The defendant’s general allegation that his fourth amendment rights were violated, without stating the circumstances under which the asserted constitutional rights were infringed, or submitting authority to substantiate the claimed violation, did not adequately raise a constitutional claim.
The defendant also claims that he relinquished his fifth amendment privilege against self-incrimination when he reported evidence of criminal conduct to the police of which he was aware and they were not. We disagree. The privilege against self-incrimination protects one from being compelled to disclose facts tending to establish criminal liability. (People ex rel. Keith v. Keith (1967), 38 Ill. 2d 405; In re Bon Voyage Travel (N.D. Ill. 1978), 449 F. Supp. 250). The defendant does not claim that he engaged in criminal activities in reliance on the proposed bargain, nor does he state that the police compelled him to disclose information which might tend to *526incriminate him. The record suggests only that the defendant voluntarily provided the police with information regarding criminal conduct which he had witnessed in the hope of obtaining favorable treatment in regard to the charges pending against him.
Finally, the defendant claims that he surrendered his sixth amendment rights when he was subjected to post-indictment interrogation outside the presence of his counsel. The sixth amendment guarantees an accused the right to the assistance of counsel after the filing of formal charges or adversarial proceedings against him. (See Maine v. Moulton (1985), 474 U.S. 159, 88 L. Ed. 2d 481, 106 S. Ct. 477.) Here, the defendant’s sixth amendment right to counsel attached to the Class X and Class 1 drug offenses with which he was charged. The defendant did not claim, however, nor does the record suggest, that agents of the prosecution questioned him about the charges pending against him as to which the right to counsel had attached. The record does suggest that the defendant met with Illinois Department of Law Enforcement agents and gave them information about drug-related activity which occurred while the defendant was acting as an agent and informant of the State.
The sixth amendment “protects the right of the accused not to be confronted by an agent of the State regarding matters as to which the right to counsel has attached without counsel being present.” (Emphasis added.) (Maine v. Moulton (1985), 474 U.S. at 177-78 n.14, 88 L. Ed. 2d at 497 n.14, 106 S. Ct. at 488 n.14.) The amendment does not prohibit police agents from questioning a defendant about criminal activity with which the defendant is not charged and as to which the sixth amendment right to counsel has not attached, simply because unrelated charges are pending against the defendant at the time. (See State v. Lale (Wis. App. 1987), 141 Wis. 2d 480.) The defendant’s sixth amend*527ment right to counsel was not violated when he talked with State agents about criminal activities which occurred while the defendant was acting as an agent and informant for the State.
As we reject the defendant’s contention that he relinquished constitutional rights in reliance on the agreement, we also reject his claim that this court’s decision in People v. Starks (1985), 106 Ill. 2d 441, requires enforcement of the agreement. In Starks, the defendant submitted to a polygraph examination allegedly in exchange for the prosecutor’s promise to dismiss the charges pending against him if he passed the test. The defendant passed the test, but the State refused to dismiss the charges. This court concluded that enforcement of the promise was necessary because the defendant surrendered his fifth amendment privilege in exchange for and in reliance on the proposed plea agreement. (106 Ill. 2d 441, 451.) Here, in contrast, the defendant did not surrender constitutionally protected interests in reliance on the agreement.
The defendant states he performed his part of the bargain in reliance on the agreement, making restoration of the pre-plea-agreement status impossible. He urges that specific enforcement is the only remedy which will adequately insure his rights under the due process clause.
Federal decisions have rejected similar arguments in circumstances where, as here, the defendant cooperated with government agents in reliance on an agreement, but did not enter a plea of guilty in reliance on it. In United States v. Coon (8th Cir. 1986), 805 F.2d 822, the defendant agreed to plead guilty to a drug offense and to cooperate with Federal authorities in narcotics investigations in exchange for the government’s promise not to bring additional charges and to make no recommendation to the court regarding the sentence. The prosecutor, *528through error, advised the defendant that the crime of which he was accused carried a maximum fine of $25,000. After the defendant fully cooperated with authorities, however, the parties learned that the maximum fine had been increased by statute to $250,000. The defendant pleaded guilty, knowing of the increased fine, and was fined $100,000. The defendant then sought to have his fine reduced to the amount discussed in the plea agreement. The defendant argued that by cooperating with the Federal agents, he had so changed his position in reliance on the erroneous statement in the plea agreement that he could not be restored to the pre-agreement status by pleading not guilty and proceeding to trial. The court rejected the defendant’s contention, explaining:
“The only change in position that can be considered ‘detrimental reliance’ is the actual entry of an involuntary guilty plea. Not until that point has the defendant been deprived of any constitutionally protected liberty interest. See Mabry, 104 S. Ct. at 2546. When, as in this case, the defendant learns of a change in the terms of a plea agreement prior to entering his plea, a detrimental reliance argument is inappropriate. At that stage, the defendant still has the option of pleading not guilty and proceeding to trial.” 805 F.2d at 825.
Similarly, in United States v. McGovern (8th Cir. 1987), 822 F.2d 739, the court rejected a defendant’s claim that specific performance of the government’s promise was necessary to redress his detrimental reliance on the plea agreement. The defendant asserted that he cooperated with the government in reliance on the agreement and provided it with otherwise unavailable information. He contended that, as a result, he suffered substantial prejudice, and that specific performance was therefore necessary because he could not be returned to his pre-plea-agreement position. The court rejected his claim, stating that, although allowing both parties to *529proceed to trial did not restore the defendant to the status quo in the sense that he could call back his year of cooperation with Federal agents, it preserved his right to a fair trial. The court concluded that none of the statements which the defendant made during the course of his plea negotiations and cooperation, nor any fruits of those statements, were used against him at his subsequent trial and that refusing to specifically enforce the plea agreement did not deprive the defendant of due process. 822 F.2d at 746.
Upon consideration of the circumstances in this case, we have concluded that the prosecutor’s stated unwillingness to carry out the alleged bargain did not deprive the defendant of due process and accordingly we reject his claim that specific performance of the bargain is the only adequate remedy. Here, as in Coon and McGovern, the defendant still has the option of pleading not guilty and going to trial. His right to a fair trial is unimpaired. We agree with one court’s observation that “[t]his fundamental right would be belittled if we held it to be an insufficient ‘remedy’ or result for a defendant who has not been induced to rely on the plea to his detriment.” Government of Virgin Islands v. Scotland (3d Cir. 1980), 614 F.2d 360, 365.
We must reject the defendant’s argument that the appellate court’s judgment should be reversed because the court improperly decided the case without oral argument. There is, of course, no constitutional right to present oral argument, and Supreme Court Rule 352 allows an appellate court to dispose of a case without oral argument, after briefs are filed, if no substantial question is presented (107 Ill. 2d R. 352(a)). This court’s decision in People v. Boyt clearly was applicable here, and we conclude that the appellate court properly determined that no substantial question was presented for its review. In any event, that we allowed leave to appeal *530from the appellate court’s judgment and have considered all arguments raised by the defendant removes any problem which might have been created when the appellate court disposed of the appeal without oral argument. Cf. People v. Mitchell (1984), 105 Ill. 2d 1, 15.
For the reasons given, the judgment of the appellate court is affirmed and the cause is remanded to the circuit court of Peoria County for further proceedings consistent with this opinion.
Appellate court affirmed; cause remanded.