delivered the opinion of the court:
Appellee, E.G., a 17-year-old woman, contracted leukemia and needed blood transfusions in the treatment of the disease. E.G. and her mother, Rosie Denton, refused to consent to the transfusions, contending that acceptance of blood would violate personal religious convictions rooted in their membership in the Jehovah’s Witness faith. Appellant, the State of Illinois, filed a neglect petition in juvenile court in the circuit court of Cook County. The trial court entered an order finding E.G. to be neglected, and appointed a guardian to consent to the transfusions on E.G.’s behalf.
The appellate court reversed the trial court in part. The court held that E.G. was a “mature minor,” and therefore could refuse the blood transfusions through the exercise of her first amendment right to freely exercise her religion. Nevertheless, the court affirmed the finding of neglect against Denton. 161 Ill. App. 3d 765.
We granted the State’s petition for leave to appeal and now affirm the appellate court’s decision in part, but on other grounds. We also remand this case to the trial court for the purpose of expunging the finding of neglect.
In February of 1987, E.G. was diagnosed as having acute nonlymphatic leukemia, a malignant disease of the white blood cells. When E.G. and her mother, Rosie Den-*102ton, were informed that treatment of the disease would involve blood transfusions, they refused to consent to this medical procedure on the basis of their religious beliefs. As Jehovah’s Witnesses, both E.G. and her mother desired to observe their religion’s prohibition against the “eating” of blood. Mrs. Denton did authorize any other treatment and signed a waiver absolving the medical providers of liability for failure to administer transfusions.
As a result of Denton’s and E.G.’s refusal to assent to blood transfusions, the State filed a neglect petition in juvenile court. At the initial hearing on February 25, 1987, Dr. Stanley Yachnin testified that E.G. had approximately one-fifth to one-sixth the normal oxygen-carrying capacity of her blood and consequently was excessively fatigued and incoherent. He stated that without blood transfusions, E.G. would likely die within a month. Dr. Yachnin testified that the transfusions, along with chemotherapy, achieve remission of the disease in about 80% of all patients so afflicted. Continued treatment, according to Dr. Yachnin, would involve the utilization of drugs and more transfusions. The long-term prognosis is not optimistic, as the survival rate for patients such as E.G. is 20 to 25%.
Dr. Yachnin stated that he discussed the proposed course of treatment with E.G. He testified that E.G. was competent to understand the consequences of accepting or rejecting treatment, and he was impressed with her maturity and the sincerity of her beliefs. Dr. Yachnin’s observations regarding E.G.’s competency were corroborated by the testimony of Jane McAtee, the associate general counsel for the University of Chicago Hospital. At the conclusion of this hearing, the trial judge entered an order appointing McAtee temporary guardian, and authorizing her to consent to transfusions on E.G.’s behalf.
*103On April 8, 1987, further hearings were held on this matter. E.G., having received several blood transfusions, was strong enough to take the stand. She testified that the decision to refuse blood transfusions was her own and that she fully understood the nature of her disease and the consequences of her decision. She indicated that her decision was not based on any wish to die, but instead was grounded in her religious convictions. E.G. further stated that when informed that she would undergo transfusions, she asked to be sedated prior to the administration of the blood. She testified that the court’s decision upset her, and said: “[I]t seems as if everything that I wanted or believe in was just being disregarded.”
Several other witnesses gave their opinions extolling E.G.’s maturity and the sincerity of her religious beliefs. One witness was Dr. Littner, a psychiatrist who has special expertise in evaluating the maturity and competency of minors. Based on interviews with E.G. and her family, Dr. Littner expressed his opinion that E.G. had the maturity level of an 18 to 21 year old. He further concluded that E.G. had the competency to make an informed decision to refuse the blood transfusions, even if this choice was fatal.
On May 18, 1987, the trial court ruled that E.G. was medically neglected, and appointed a guardian to consent to medical treatment. The court felt this was in E.G.’s best interests. The court did state, however, that E.G. was “a mature 17-year-old individual,” that E.G. reached her decision on an independent basis, and that she was “fully aware that death [was] assured absent treatment.” The court noted that it considered E.G.’s maturity and the religion of her and her parents, and that it gave great weight to the wishes of E.G. Nevertheless, the court felt that the State’s interest in this case was greater than the interest E.G. and her mother *104had in refusing to consent to treatment. The court concluded its ruling by encouraging E.G. to appeal.
On appeal, the order of the trial court pertaining to E.G.’s right to refuse treatment was vacated in part and modified in part. (161 Ill. App. 3d 765.) The appellate court observed that this court, in In re Estate of Brooks (1965), 32 Ill. 2d 361, held that an adult Jehovah’s Witness had a first amendment right to refuse blood transfusions. The appellate court then extended the holding in Brooks to include “mature minors,” deriving this extension from cases in which the United States Supreme Court allowed “mature minors” to consent to abortions without parental approval through the exercise of constitutional privacy rights. (See City of Akron v. Akron Center for Reproductive Health, Inc. (1983), 462 U.S. 416, 76 L. Ed. 2d 687, 103 S. Ct. 2481; Bellotti v. Baird (1979), 443 U.S. 622, 61 L. Ed. 2d 797, 99 S. Ct. 3035.) Although the United States Supreme Court has not broadened this constitutional right of minors beyond abortion cases, the appellate court found such an extension “inevitable.” Relying on our Emancipation of Mature Minors Act (Ill. Rev. Stat. 1987, ch. 40, par. 2201 et seq.), the court held that a mature minor may exercise a constitutional right to refuse medical treatment.
The appellate court noted that E.G., at the time of trial, was only six months shy of her eighteenth birthday, and that the trial court believed E.G. to be a mature individual. Based on these facts, the appellate court declared that E.G. was partially emancipated and therefore had the right to refuse transfusions. The court, however, affirmed the finding of neglect against Denton, E.G.’s mother.
We granted the State’s petition for leave to appeal under our Rule 315 (107 Ill. 2d R. 315). This case presents several issues for our consideration: (1) whether this appeal should be dismissed as moot, since E.G. *105turned 18 on November 25, 1987, and is no longer a minor; (2) whether a minor has a right to refuse medical treatment and if so, how this right may be exercised; and (3) whether the trial court’s finding of neglect against Denton should stand.
Both parties agree that although this case is technically moot, it should not be dismissed. Normally, this court will not adjudicate an appeal where a live controversy no longer exists. (People ex rel. Black v. Dukes (1983), 96 Ill. 2d 273, 276; Madison Park Bank v. Zagel (1982), 91 Ill. 2d 231, 234-35.) Here, since E.G. has reached her eighteenth birthday, she can no longer be adjudged a neglected minor for the purpose of the Juvenile Court Act of 1987. (See Ill. Rev. Stat. 1987, ch. 37, par. 802 — 3.) We do not review cases merely to guide future litigation or establish precedent. (Madison Park Bank, 91 Ill. 2d at 235.) Where no present controversy exists between the parties, a case should be dismissed as moot. 91 Ill. 2d at 235.
Nevertheless, there are exceptions to the mootness doctrine. One departure from the usual rule occurs when a case presents an issue of substantial public interest. (In re Estate of Brooks (1965), 32 Ill. 2d 361, 364-65; People ex rel. Wallace v. Labrenz (1952), 411 Ill. 618, 622-23.) In determining whether a case exhibits the requisite degree of public interest, we look to “the public or private nature of the question presented, the desirability of an authoritative determination for the future guidance of public officers, and the likelihood of future recurrence of the question.” (411 Ill. at 622.) We note that both Labrenz and Brooks involved Jehovah’s Witness members who refused to consent to blood transfusions. In Labrenz and Brooks, this court concluded that significant public interest existed and, although the controversies were moot, decided the cases on the merits. Similarly, we find that the case before us meets the public interest excep*106tion criteria quoted above from Labrenz. Consequently, we will consider the issues raised by the parties in this case.
The paramount issue raised by this appeal is whether a minor like E.G. has a right to refuse medical treatment. In Illinois, an adult has a common law right to refuse medical treatment, even if it is of a life-sustaining nature. (See In re Estate of Longeway (1989), 133 Ill. 2d 33.) This court has also held that an adult may refuse life-saving blood transfusions on first amendment free exercise of religion grounds. (In re Estate of Brooks (1965), 32 Ill. 2d 361.) An infant child, however, can be compelled to accept life-saving medical treatment over the objections of her parents. (People ex rel. Wallace v. Labrenz (1952), 411 Ill. 618.) In the matter before us, E.G. was a minor, but one who was just months shy of her eighteenth birthday, and an individual that the record indicates was mature for her age. Although the age of majority in Illinois is 18, that age is not an impenetrable barrier that magically precludes a minor from possessing and exercising certain rights normally associated with adulthood. Numerous exceptions are found in this jurisdiction and others which treat minors as adults under specific circumstances.
In Illinois, our legislature enacted “An Act in relation to the performance of. medical, dental or surgical procedures on and counseling for minors” (the Consent by Minors to Medical Operations Act), which grants minors the legal capacity to consent to medical treatment in certain situations. (See Ill. Rev. Stat. 1987, ch. 111, par. 4501 et seq.) For example, a minor 12 years or older may seek medical attention on her own if she believes she has venereal disease or is an alcoholic or drug addict. (Ill. Rev. Stat. 1987, ch. 111, par. 4504.) Similarly, an individual under 18 who is married or pregnant may validly consent to treatment. (Ill. Rev. Stat. 1987, ch. 111, par. *1074501.) Thus, if E.G. would have been married she could have consented to or, presumably, refused treatment. Also, a minor 16 or older may be declared emancipated under the Emancipation of Mature Minors Act (Ill. Rev. Stat. 1987, ch. 40, par. 2201 et seq.), and thereby control his or her own health care decisions. These two acts, when read together in a complementary fashion, indicate that the legislature did not intend that there be an absolute 18-year-old age barrier prohibiting minors from consenting to medical treatment.
In an analogous area of law, no “bright line” age restriction of 18 exists either. Under the Juvenile Court Act, individuals much younger than 18 may be prosecuted under the Criminal Code, if circumstances dictate. (See Ill. Rev. Stat. 1987, ch. 37, par. 805 — 4.) Furthermore, to be convicted of many of the offenses in the Criminal Code, a trier of fact would have to find that a minor had a certain mental state at the time the alleged crime was committed. Implied in finding this mental state would be an acknowledgment that a minor was mature enough to have formulated this mens rea. Consequently, the Juvenile Court Act presupposes a “sliding scale of maturity” in which young minors can be deemed mature enough to possess certain mental states and be tried and convicted as adults. This act reflects the common law, which allowed infancy to be a defense to criminal acts. The infancy defense at common law was “based upon an unwillingness to punish those thought to be incapable of forming criminal intent and not of an age where the threat of punishment could serve as a deterrent.” (Emphasis added.) (W. LaFave & A. Scott, Criminal Law §46 (1972).) When a minor is mature enough to have the capacity to formulate criminal intent, both the common law and our Juvenile Court Act treat the minor as an adult.
*108Another area of the law where minors are treated as adults is constitutional law, including the constitutional right of abortion. The United States Supreme Court has adopted a mature minor doctrine, which allows women under the age of majority to undergo abortions without parental consent. (See City of Akron v. Akron Center for Reproductive Health, Inc. (1983), 462 U.S. 416, 76 L. Ed. 2d 687, 103 S. Ct. 2481; Bellotti v. Baird (1979), 443 U.S. 622, 61 L. Ed. 2d 797, 99 S. Ct. 3035.) In the abortion rights context, the Court has noted: “Constitutional rights do not mature and come into being magically only .when one attains the state-defined age of majority. Minors, as well as adults, are protected by the Constitution and possess constitutional rights.” (Planned Parenthood of Central Missouri v. Danforth (1976), 428 U.S. 52, 74, 49 L. Ed. 2d 788, 808, 96 S. Ct. 2831, 2843.) Moreover, children enjoy the protection of other constitutional rights, including the right of privacy (Carey v. Population Services International (1977), 431 U.S. 678, 52 L. Ed. 2d 675, 97 S. Ct. 2010), freedom of expression {Tinker v. Des Moines Independent Community School District (1969), 393 U.S. 503, 21 L. Ed. 2d 731, 89 S. Ct. 733), freedom from unreasonable searches and seizures {New Jersey v. T.L.O. (1985), 469 U.S. 325, 83 L. Ed. 2d 720, 105 S. Ct. 733), and procedural due process (In re Application of Gault (1967), 387 U.S. 1, 18 L. Ed. 2d 527, 87 S. Ct. 1428). Nevertheless, the Supreme Court has not held that a constitutionally based right to refuse medical treatment exists, either for adults or minors. While we find the language from the cases cited above instructive, we do not feel, as the appellate court did, that an extension of the constitutional mature minor doctrine to the case at bar is “inevitable.” These cases do show, however, that no “bright line” age restriction of 18 is tenable in restricting the rights of mature minors, whether the rights be based on constitu*109tional or other grounds. Accordingly, we hold that in addition to these constitutionally based rights expressly delineated by the Supreme Court, mature minors may possess and exercise rights regarding medical care that are rooted in this State’s common law.
The common law right to control one’s health care was also the basis for the right of an incompetent patient to refuse life-sustaining treatment through a surrogate in In re Estate of Longeway, 133 Ill. 2d at 45-46. While the issue before us in this case is not exactly the same as in Longeway, the foundation of the common law right here and in Longeway is the same. We see no reason why this right of dominion over one’s own person should not extend to mature minors. Furthermore, we find support for this conclusion in a decision of one of our sister States. In Cardwell v. Bechtol (Tenn. 1987), 724 S.W.2d 739, the Tennessee Supreme Court held that a mature minor had the capacity to consent to medical procedures based on the common law of that State. The court noted that the mature minor doctrine is not a recent development in the law: “ [Recognition that minors achieve varying degrees of maturity and responsibility (capacity) has been part of the common law for well over a century.” 724 S.W.2d at 744-45.
In Cardwell, the Tennessee court held that a minor 17 years, 7 months old was mature enough to consent to medical treatment. We note that in other jurisdictions, courts have ordered health care for minors over the objections of the minors’ parents. These cases, however, involve minors who were younger than E.G. or the minor in Cardwell. (See, e.g., In re Eric B. (1987), 189 Cal. App. 3d 996, 235 Cal. Rptr. 22 (six-year-old boy); In the Interest of D.L.E. (Colo. 1982), 645 R2d 271 (16 year old); In re Ivey (Fla. App. 1975), 319 So. 2d 53 (one-month-old infant); Morrison v. State (Mo. App. 1952), 252 S.W.2d 97 (12-day-old child); People v. Perricone *110(1962), 37 N.J. 463, 181 A.2d 751 (infant); In re Custody of a Minor (1978), 375 Mass. 733, 379 N.E.2d 1053 (two-year-old girl); In re Willmann (1986), 24 Ohio App. 3d 191, 493 N.E.2d 1380 (seven-year-old boy); In re Hamilton (Tenn. App. 1983), 657 S.W.2d 425 (12-year-old girl); Mitchell v. Davis (Tex. Civ. App. 1947), 205 S.W.2d 812 (12-year-old boy).) Moreover, the issue in the above cases was not whether a minor could assert a right to control medical treatment decisions, but whether the minor’s parents could refuse treatment on behalf of their child. Here, E.G. contends she was mature enough to have controlled her own health care. We find that she may have done so if indeed she would have been adjudged mature.
The trial judge must determine whether a minor is mature enough to make health care choices on her own. An exception to this, of course, is if the legislature has provided otherwise, as in the Consent by Minors to Medical Operations Act (Ill. Rev. Stat.. 1987, ch. 111, par. 4501 et seq.). We feel the intervention of a judge is appropriate for two reasons.
First, Illinois public policy values the sanctity of life. (In re Estate of Longeway, 133 Ill. 2d at 51; Siemieniec v. Lutheran General Hospital (1987), 117 Ill. 2d 230, 249.) When a minor’s health and life are at stake, this policy becomes a critical consideration. A minor may have a long and fruitful life ahead that an immature, foolish decision could jeopardize. Consequently, when the trial judge weighs the evidence in making a determination of whether a minor is mature enough to handle a health care decision, he must find proof of this maturity by clear and convincing evidence.
Second, the State has a parens patriae power to protect those incompetent to protect themselves. (Longeway, 133 Ill. 2d at 52; 27 Am. Jur. 2d Equity §69 (1966).) “[I]t is well-settled that the State as parens pa- *111 trim has a special duty to protect minors and, if necessary, make vital decisions as to whether to submit a minor to necessary treatment where the condition is life threatening, as wrenching and distasteful as such actions may be.” (In re Hamilton (Tenn. App. 1983), 657 S.W.2d 425, 429.) The State’s parens patriae power pertaining to minors is strongest when the minor is immature and thus incompetent (lacking in capacity) to make these decisions on her own. The parens patriae authority fades, however, as the minor gets older and disappears upon her reaching adulthood. The State interest in protecting a mature minor in these situations will vary depending upon the nature of the medical treatment involved. Where the health care issues are potentially life threatening, the State’s parens patriae interest is greater than if the health care matter is less consequential.
Therefore, the trial judge must weigh these two principles against the evidence he receives of a minor’s maturity. If the evidence is clear and convincing that the minor is mature enough to appreciate the consequences of her actions, and that the minor is mature enough to exercise the judgment of an adult, then the mature minor doctrine affords her the common law right to consent to or refuse medical treatment. As we stated in Longeway, however, this common law right is not absolute. The right must be balanced against four State interests: (1) the preservation of life; (2) protecting the interests of third parties; (3) prevention of suicide; and (4) maintaining the ethical integrity of the medical profession. (Longeway, 133 Ill. 2d at 48, quoting Superintendent of Belchertown State School v. Saikewicz (1977), 373 Mass. 728, 741, 370 N.E.2d 417, 425.) Of these four concerns, protecting the interests of third parties is clearly the most significant here. The principal third parties in these cases would be parents, guardians, adult siblings, and other relatives. If a parent or guardian opposes an *112unemancipated mature minor’s refusal to consent to treatment for a life-threatening health problem, this opposition would weigh heavily against the minor’s right to refuse. In this case, for example, had E.G. refused the transfusions against the wishes of her mother, then the court would have given serious consideration to her mother’s desires.
Nevertheless, in this case both E.G. and her mother agreed that E.G. should turn down the blood transfusions. They based this refusal primarily on religious grounds, contending that the first amendment free exercise clause entitles a mature minor to decline medical care when it contravenes sincerely held religious beliefs. Because we find that a mature minor may exercise a common law right to consent to or refuse medical care, we declin.e to address the constitutional issue. See Longeway, 133 Ill. 2d at 44; see also In re Application of Rosewell (1983), 97 Ill. 2d 434, 440 (constitutional questions should not be considered if a case can be decided on other grounds).
The final issue we must address is whether the finding of neglect entered against Rosie Denton, E.G.’s mother, should stand. If the trial judge had ruled that E.G. was a mature minor, then no finding of neglect would be proper. Although the trial judge was impressed with E.G.’s maturity and sincerity, the judge did not explicitly hold that E.G. was a mature minor. The trial judge, guided only by the law as it existed prior to this opinion, rightly felt that he must protect the minor’s health and well-being. This case is one of first impression with this court. Therefore, the trial judge had no precedent upon which to base a mature minor finding. Because E.G. is no longer a minor, nothing would be gained by remanding this case back to the trial court for an explicit determination of E.G.’s maturity. Nevertheless, since the trial judge did not have any clear guid*113anee on the mature minor doctrine, we believe that the finding of neglect should not stand. Accordingly, we affirm the appellate court in part and reverse in part, and remand this case to the circuit court of Cook County for the sole purpose of expunging the finding of neglect against Denton.
Appellate court affirmed in part and reversed in part; circuit court reversed; case remanded with directions.