Defendant, a mildly retarded adult, appeals from an order of the district court revoking his probation. He claims that (1) his probation warrant should be declared void because he lacked the capacity to sign it, or that it not be enforced because of the doctrine of impossibility, (2) the court erred by revoking probation without holding an additional competency hearing and without notifying defendant’s protective services guardian, (3) warrantless searches of his living quarters and person by probation officers violated his constitutional privacy rights, and (4) a probation condition prohibiting possession of photographs of children violated his freedoms of speech and religion. We affirm.
*549In 1986, defendant was charged with sexually assaulting a four-year-old girl. In February 1987, after evaluation and hearing, he was found competent to stand trial. After additional evaluation and a hearing in December 1987, the court again found defendant competent to stand trial. The court concluded that defendant had a firm knowledge of the facts concerning his actions and whereabouts, that he was able to assist his attorney in locating and examining witnesses, that he was able to discern distortions and misstatements in testimony, that he could make decisions in response to carefully explained alternatives concerning his defense, that his comprehension improved with explanation, and that there was no indication that his condition would worsen under the stress of trial.
Prior to the second competency proceeding, the court granted defendant’s petition for protective services pursuant to 18 V.S.A. §§ 9301-9317. The court found that he was unable to provide for his own needs and appointed a protective services worker. The court further found that defendant had “no understanding of the concept of a contract or any of the implications involved in entering into a contract.”
In January 1988, pursuant to a plea agreement, defendant pled nolo contendere and was sentenced to serve three-to-eight years. The court suspended all but 153 days and placed defendant on probation with special conditions that prohibited him from possessing dolls, dolls’ or children’s clothing, and pictures of children. In February 1989, probation officers and a state police officer searched defendant’s room and workshop at his supervised residence and found a knife, dolls, children’s clothing, and hundreds of pictures of children. In March 1989, while the resulting violation of probation was pending, defendant pled nolo contendere to a charge of lewd and lascivious conduct for exposing himself to young girls. For that offense, he received a sentence of zero-to-four years, all suspended. For the violation of probation, he was sentenced to serve the original underlying term of three-to-eight years, all suspended but 161 days with credit awarded for 153 days already served. New conditions were added to defendant’s probation warrant, including that he not possess any firearm or other deadly weapon and that he submit to a “body, clothing, [and] residential search as required.”
*550Defendant signed his probation warrants after both sentencings and initialed each condition following explanation by a probation officer. His protective services worker was not present when he signed the warrant. The court found that defendant understood his probation conditions when imposed and that those conditions were given significant attention during the pendency of his probation. For example, at all weekly meetings with defendant, his probation officers read each special condition, explained its meaning, and discussed it with him. On each visit, they required him to write out his “rules” until they were committed to memory. Once defendant was placed in a private residential setting in early 1989, his supervisor, who has a master’s degree in education and counseling, reviewed defendant’s special conditions with him daily and emphasized that his living quarters and workshop area were subject to frequent, unannounced searches.
After defendant displayed symptoms similar to those exhibited prior to his earlier violation of probation — refusing to perform tasks, complaining about restrictions, and displaying general agitation — his supervisor searched defendant’s workshop area looking for pictures of children. In defendant’s file cabinet, the supervisor found a fully operational pistol with clips and ammunition, which had been left elsewhere in the residence a year earlier by an acquaintance of the supervisor. Probation officers then searched defendant’s living quarters and workshop area. They found photographs of female children, magazines and newspapers with pictures of young children, a child’s T-shirt, a doll’s cap, children’s records, a wrench, a chain, a hand gardening tool, a ten-inch drill bit, a plastic covered braided wire, and single-edged razor blades. A probation officer strip-searched defendant but found nothing.
In connection with his revocation hearing, defendant moved to suppress introduction of physical evidence, arguing that the warrantless searches violated his constitutional privacy rights. He also moved to suppress statements he made, arguing that he had not waived his right to remain silent and to consult with an attorney. The court denied these motions, concluding that the state’s interest in protecting the community permitted a degree of encroachment on defendant’s privacy rights, that defendant had consented to the search when he signed his probation war*551rant, and that he had not been in custody when the statements were made. In December 1989, the court found that defendant had violated three conditions of his probation and later sentenced him to serve both underlying sentences of three-to-eight and zero-to-four years consecutively.
I.
Defendant raises two contract-based challenges to the validity of his probation warrant. Defendant first argues that a probation warrant is a contract, which in this case was void and unenforceable because it was not signed by the protective services worker to whom the court had delegated defendant’s power to contract. We disagree.
The provisions of 18 V.S.A. § 9310(a)(2), which grant a guardian “power to approve or withhold approval of any contract . . . which the retarded person wishes to make,” do not require the guardian’s signature on a defendant’s probation warrant. Although we have termed probation warrants “contracts,” State v. Whitchurch, 155 Vt. 134, 139, 577 A.2d 690, 693 (1990), the purposes of a probation warrant illustrate its difference from an ordinary contract. A probation warrant serves to give a defendant fair notice of what conduct may constitute a probation violation, thereby resulting in defendant’s loss of liberty. State v. Peck, 149 Vt. 617, 619, 547 A.2d 1329, 1331 (1988). Section 9310(a)(2), however, refers to contracts that “the retarded person wishes to make.” Here, defendant chose to plead guilty and accept probation to avoid possible incarceration. Although defendant may have “wished” to make the probation contract with the court, his choice was forced and the result of his criminal conduct. We conclude that a probation warrant is not the type of contract contemplated by § 9310(a)(2).
Second, defendant argues that he lacked the ability to comprehend or comply with his conditions of probation; therefore, performance of the probation warrant was impossible from the outset, and this Court should not enforce the contract.1 As *552stated above, a probation warrant differs from an ordinary contract. Moreover, the evidence does not support defendant’s argument that the performance of the warrant was impossible. Instead, the court took pains to fashion unique probation conditions that were suited to defendant’s particular situation in order to create the best chance for his rehabilitation. Moreover, as previously noted, the probation officers repeatedly discussed these conditions with defendant and helped him commit them to memory.
Nor does defendant’s alleged inability to comply with the conditions at the time of the violation bar revocation of his probation. Probation is intended to allow a defendant an opportunity for rehabilitation at the same time it protects society. See United States v. O’Sullivan, 421 F. Supp. 300, 302 (S.D.N.Y. 1976) (despite rehabilitative purposes of probation, it will be revoked if defendant is a danger to society). The purpose of a revocation hearing is not to determine defendant’s culpability, but rather to decide “whether the alternatives to incarceration which have been made available to a defendant remain viable for him.” People ex rel. Gallagher v. District Court, 591 P.2d 1015, 1017 (Colo. 1978) (en banc). Revocation will result when the continuation of probation conditions would be at odds with the need to protect the public and society’s interest in rehabilitation — in other words, when the rehabilitative purposes of probation have failed and defendant is a threat to society. Trumbly v. State, 515 P.2d 707, 709 (Alaska 1973); People v. Allegri, 487 N.E.2d 606, 607 (Ill. 1985); State v. Hutchison, 580 N.E.2d 34, 36 (Ohio Ct. App. 1989); see 28 V.S.A. § 303 (stating grounds for revocation). Thus, many courts have ruled that a plea of not guilty by reason of insanity is not a defense in probation revocation hearings because defendant’s personal culpability is not at issue. See, e.g., Trumbly, 515 P.2d at 708-09 *553(insanity defense irrelevant in probation revocation hearing); People v. Breaux, 161 Cal. Rptr. 653, 657 (Ct. App. 1980) (insanity not a defense to probation violation, but relevant to probation revocation or modification); People ex rel. Gallagher, 591 P.2d at 1017 (sanity a factor only in determining continued availability of probation); Allegri, 487 N.E.2d at 608 (insanity defense has no bearing on relevant issue of whether defendant a danger to society); Hutchison, 580 N.E.2d at 36 (issue in revocation hearing is whether probation should remain available, not whether defendant responsible for acts alleged). If a defendant’s subsequent inability to comply with a probation condition barred revocation, this effectively would limit a sentencing court’s flexibility to fashion appropriate probation conditions. Courts would sentence defendants to unnecessary periods of imprisonment whenever there appeared to be a risk of violation because of questionable ability to comply. Allegri, 487 N.E.2d at 609.
Although defendant’s alleged inability to comply with the conditions at the time of violation does not bar revocation, his mental ability is a relevant factor in deciding whether the continuation of his probation will be at odds with the need to protect society. See State v. O’Meal, 569 P.2d 249, 251 (Ariz. Ct. App. 1977) (time of probation violation relevant to viability of continued probation); Breaux, 161 Cal. Rptr. at 657; People ex rel. Gallagher, 591 P.2d at 1017. In this case, the court took defendant’s mental capacity into consideration at the revocation hearing. The court’s decision was not an abuse of discretion. See State v. Therrien, 140 Vt. 625, 627, 442 A.2d 1299, 1301 (1982) (if violation is established, court has discretion to revoke probation and impose original sentence under 28 V.S.A. § 304).
II.
Defendant raises two issues regarding the revocation hearing. First, he argues that the trial court erred by subjecting him to revocation proceedings without notice to, or the presence of, his protective services worker.
A judge found defendant competent to stand trial in December 1987 following extensive evaluation and a contested hearing. At the time of that hearing, the judge was fully aware of *554defendant’s need for protective services because he himself had appointed a protective services worker in May 1987 after concluding that defendant was unable to provide for his own needs. We agree with the judge’s implicit conclusion that defendant’s need for protective services, as determined pursuant to 18 V.S.A. § 9309, could not bar his full participation in criminal proceedings when, as here, a defendant is subsequently found competent to stand trial.
Once defendant was found competent to stand trial and face criminal consequences for his conduct, due process considerations precluded the involvement of his protective services worker. See State v. Ladd, 139 Vt. 642, 644, 433 A.2d 294, 295 (1981) (retention of guardian ad litem for competent adult violates defendant’s due process rights). The protective services proceedings did not alter the finding of competency because the two proceedings relied on distinct criteria. Protective services focus on a mentally retarded person’s need for supervision and protection. 18 V.S.A. § 9309(e)(4). In contrast, a competency determination measures whether a defendant is capable of understanding the criminal proceedings and consulting with an attorney. Godinez v. Moran, — U.S. —, ■ — ■, 113 S. Ct. 2680, 2685 (1993). Moreover, a criminal proceeding, including a revocation hearing, is not the type of “judicial action” which a guardian may “commence or defend” under 18 V.S.A. § 9310(a)(3), and consequently, the statute does not provide for the guardian’s participation in defendant’s criminal proceeding. There was no error.
Second, defendant argues that the trial court erred by failing to conduct a new competency hearing before commencing the revocation proceeding. We find no error in the court’s decision to rely on the prior finding of competency because the court had no indication of the need for a new determination.
The trial court has a duty to order a psychiatric examination and conduct a competency hearing if there is “reason to believe that [the defendant] may be incompetent to stand trial.” 13 V.S.A. § 4817(b). Moreover, the same standard of competency applies to defendants who stand trial as to those who plead guilty. Moran, — U.S. at —, 113 S. Ct. at 2686. Once a defendant has been found competent, the trial court must be *555alert to changed circumstances that would indicate the need for a new determination of competency. Drope v. Missouri, 420 U.S. 162, 181 (1975).
Here, the court had no indication before it of any change warranting a new competency hearing. The court considered the issue and concluded that it would leave the earlier determination of competency in place “absent something more than [defense counsel’s] feeling about it.” In finding defendant competent in December 1987, the court concluded that his comprehension improved with explanation. The evidence demonstrated that between 1987 and the revocation proceeding defendant received extensive explanation regarding his conditions and the consequences for violating them. Although defense counsel told the court that she had trouble communicating with defendant, she did not point to any changed circumstances that would have indicated to the court the need for a new inquiry into defendant’s competence, and we can find no such indication in the record. Cf. State v. Pierce, 569 P.2d 865, 869 (Ariz. Ct. App. 1977) (nothing in record to support need for second competency inquiry prior to sentencing); State v. Herat, 342 N.E.2d 34, 38 (Ill. 1976) (record did not reflect changed circumstances that would have alerted trial judge to need for new competency hearing). Moreover, defense counsel never requested a new competency hearing prior to the revocation proceedings. We conclude that the court did not err when it decided not to order a third competency hearing prior to commencing revocation proceedings.
III.
Defendant claims that the warrantless searches of his living quarters and person violated rights guaranteed by the Fourth Amendment to the United States Constitution2 and Chapter I, Article 11 of the Vermont Constitution.3 Preliminarily, defend*556ant argues that he was not competent to waive his privacy-rights when he signed his probation warrant. We need not rule on this issue because, unlike the trial court, we do not rely on defendant’s consent to his probation terms. Even when a probationer signs a blanket condition agreeing to future searches, he may continue to enjoy residual privacy rights deserving some constitutional protection. Cf. State v. Emery, 156 Vt. 364, 369, 593 A.2d 77, 79 (1991) (probationers are subject to restrictions not imposed on ordinary persons, but only to the extent they serve the ends of probation).
The United States Supreme Court has held that searches of probationers’ homes pursuant to a state regulation are permissible under the Fourth Amendment where the officer possesses “reasonable grounds” for the search. Griffin v. Wisconsin, 483 U.S. 868, 872 (1987). In such situations, the search need not satisfy the higher probable cause standard.4 Id. at 873. The Court applied this lesser standard because it acknowledged that the special needs of the state in administering probation require balancing the rehabilitative needs of probationers against concerns for protection of the community. Id. at 873-74.
Here, probation officers acted pursuant to a condition of probation rather than a state regulation. As this Court has noted, however, when probation conditions are “supported by the findings and are narrowly tailored to fit the circumstances of the individual probationer ... probation searches based on reasonable suspicion can have the same indicia of reasonableness as the search upheld in Griffin.” State v. Moses, 159 Vt. 294, 304-05, 618 A.2d 478, 484 (1992) (citations omitted). Such specific and narrowly tailored probation conditions provide guidance to probation officers similar to that provided by the regulatory scheme in Griffin. United States v. Giannetta, 909 F.2d 571, 575 (1st Cir. 1990).
*557Ideally, the probation condition itself will limit the search to the specific requirements for the supervision of the particular defendant. See United States v. Schoenrock, 868 F.2d 289, 291-92 (8th Cir. 1989) (where defendants pled guilty to conspiracy to distribute cocaine, probation condition allowing warrantless searches was limited to submission to chemical testing for drugs and random searches for alcohol and controlled substances). In some instances, however, such narrow probation conditions are not appropriate or possible. The United States Court of Appeals for the First Circuit upheld a search based on a probation term that required that the defendant “at all times during his period of probation, readily submit to a search of his residence ... by his supervising probation officer, upon the officer’s request.” Giannetta, 909 F.2d at 573. The court held that the defendant’s guilty plea to the complex offense of drug trafficking and his admitted strong attraction to the excitement of crime posed “more than an average risk that [the defendant] would revert to his prior criminal ways.” Id. at 575-76. Because of this high risk of recidivism, the trial court had expressed concern that the defendant be subject to rigorous scrutiny when it imposed the probation condition.
As in Giannetta, in this case there was ample evidence that defendant posed “more than an average risk” of repeating his offense. The court emphasized that defendant’s chance for repeating his offense was high because of the dual nature of his condition: mental retardation and sexual deviancy. The combination of these two factors resulted in compulsive sexual behavior without awareness of the consequences of this behavior. Moreover, defendant had been sexually abused as a child.
The plea agreement hearing focused on defendant’s need for a special rehabilitation program in the absence of an appropriate program for mentally retarded sex offenders. All of the witnesses at the hearing noted the concern of protecting society from the high risk that defendant would repeat the offense. As one witness stated, “[Defendant] will be aroused by children the rest of his life----[W]e do not expect to cure his compulsive behavior.” Instead, the focus of the rehabilitation would be to teach defendant to control his compulsive urges. The court stated: “The Department of Corrections is going to be asked to supervise this defendant. It seems to me that we’re putting the *558department in an extremely difficult position to ask them to supervise someone who has a definite need and yet not to give them the resources.” Thus, the evidence of the high risk that defendant would repeat his offense supported the condition allowing a search by the probation officer.
Moreover, the court’s expressed concerns regarding defendant’s compulsive sexual urges provided guidance to the probation officer as to the purposes of any search that would be conducted. See Giannetta, 909 F.2d at 575-76. These findings provided sufficient guidance to the officers conducting the search to meet the test set forth in Moses that the condition be narrowly tailored to fit the circumstances of the individual probationer.
The probation condition, however, on its face allowed a search by the probation officer with or without reasonable suspicion. This error could invalidate the probation term under Griffin. The same flaw in the probation condition was present in Giannetta. Id. at 576. This Court adopts the holding in Giannetta, which states: “Although this flaw theoretically renders the probation search condition overbroad, the absence of a reasonableness limitation is not objectionable so long as the decision to search was in fact narrowly and properly made on the basis of reasonable suspicion . . . .” Id. Under Griffin, the officers must have had “reasonable grounds” to conduct the searches. Griffin, 483 U.S. at 872. In the present case, defendant’s agitation — similar to behavior he exhibited prior to his earlier probation violation — triggered the initial search by his supervisor. Once she found the gun, which defendant subsequently denied having, the probation officers had more than reasonable grounds to conduct a thorough search of his living quarters. Thus, although the probation condition in this case is flawed, this error was overcome because the officers had reasonable suspicion to conduct the search, and these searches did not violate defendant’s Fourth Amendment rights.
Defendant also argues that his Fourth Amendment rights were violated by the officers’ strip search of his person. We need not reach this issue as no evidence was produced from this search.
Defendant asks this Court to construe Chapter I, Article 11 of the Vermont Constitution to require a warrant for the *559searches of his home and person. Although we are mindful that limits must be placed on such searches and that consent to future searches “as required” does not permit unfettered intrusions into the private lives of probationers, we find that the “reasonable grounds” standard establishes the proper safeguard. We are persuaded by the reasoning of Griffin: that the special needs of the state in administering its probation program creates an exception to the warrant requirement and permits a degree of “impingement upon privacy that would not be constitutional if applied to the public at large.” 483 U.S. at 875.
Despite the absence of the word “unreasonable” from the text of Article 11, it has been construed consistently to forbid only unreasonable searches and seizures; reasonable searches are constitutionally permissible. State v. Record, 150 Vt. 84, 85-86, 548 A.2d 422, 423 (1988). A warrantless search may be reasonable: “Article Eleven does not mandate an absolute prohibition against searches and seizures undertaken without a proper warrant.” Id. We apply the reasonableness standard here, but decline to require a warrant because the terms of probation and the court’s expressed concerns provided sufficient guidance to the probation officers regarding the purposes and parameters of allowable searches.
We have previously held that in the prison setting, in which special needs of the state make the warrant and probable cause standard impracticable, the state must adhere to certain administrative safeguards to protect the residuum of inmate privacy. State v. Berard, 154 Vt. 306, 314, 576 A.2d 118, 122-23 (1990) (mandating administrative guidelines to govern routine, random, warrantless searches of inmates). While the privacy rights of probationers are arguably greater than those of inmates, the needs of the state in administering probation, as opposed to a correctional facility, remain strong. Without walls, the probation system strives to protect the public while it attempts to rehabilitate its participants. We hold that, if a probation term provides for warrantless searches and the terms of probation are narrowly tailored to fit the circumstances of the individual probationer, the Griffin “reasonable grounds” standard strikes the proper balance between probationer privacy rights and public protection concerns. If officers have reasonable grounds, as they did here, to conduct a search under the *560authority of a condition of probation, Article 11 does not require a search warrant.
IV.
Defendant argues for the first time on appeal that the condition of probation that prohibited him from possessing “any photographs of children under the age of 18” violated his freedoms of speech and religion guaranteed by the First Amendment to the United States Constitution and Chapter I, Article 13 of the Vermont Constitution. Because defendant failed to raise this issue below, we confine our analysis to plain error. State v. Mace, 154 Vt. 430, 436, 578 A.2d 104, 108 (1990) (absent plain error, this Court will not consider probationer’s constitutional claims raised for the first time on appeal). We find none.
“Probation conditions may impact upon a probationer’s First Amendment rights so long as the conditions have a reasonable nexus with rehabilitation of the defendant and protection of the public.” Id. The court has broad discretion in setting conditions of probation, 28 V.S.A. § 252(a), and may require a probationer to satisfy “any .. . conditions reasonably related to his rehabilitation.” Id. § 252(b)(13). Here, an expert testified that people with defendant’s problems often collect pictures of children because they are “extremely important to what sexually turns them on.” He further testified that defendant had “extreme difficulty” controlling his sexual behavior relative to children. We find the disputed condition reasonably related both to defendant’s rehabilitation and protection of the public. Moreover, the condition was not “unduly restrictive of [defendant’s] liberty or autonomy,” Whitchurch, 155 Vt. at 137, 577 A.2d at 692, as we can find no evidence that he retained the pictures for religious or expressive purposes.
Affirmed.
The dissent states that this opinion “glosses over the real issue presented— whether defendant was competent to enter into guilty pleas and probation warrants.” The United States Supreme Court has recently decided that the *552competency standard for pleading guilty is the same as the competency standard for standing trial. See Godinez v. Moran, — U.S. —, • — , 113 S. Ct. 2680, 2686 (1993). Defendant has not provided any reasons why the Vermont Constitution’s due process protections would guarantee a higher standard of competency; therefore, defendant has waived the issue because it has not been squarely raised before this Court. See R. Brown & Sons, Inc. v. International Harvester Corp., 142 Vt. 140, 142, 453 A.2d 83, 84 (1982) (issues not briefed on appeal are waived).
The Fourth Amendment states, in part: “The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause.”
Article Eleven states: “That the people have a right to hold themselves, their houses, papers, and possessions, free from search or seizure; and therefore warrants, without oath or affirmation . . . ought not to be granted.”
In Vermont, the standard for probable cause resembles the reasonable grounds test adopted here. State v. Towne, 158 Vt. 607, 613-16, 615 A.2d 484, 488-89 (1992) (rejecting “more likely than not” standard and holding that probable cause can be based on the reasonable inference of criminal behavior). The'important inquiry is whether the determination of reasonable grounds should have been made by the officers who searched, or rather by a “neutral and detached magistrate.” Johnson v. United States, 333 U.S. 10, 15 (1948).