delivered the opinion of the court:
A St. Clair County grand jury indicted Carl Burpo, a medical doctor, for various sex offenses, including eight counts of criminal sexual assault in violation of section 12 — 13(a)(2) of the Criminal Code of 1961 (Ill. Rev. Stat. 1991, ch. 38, par. 12 — 13(a)(2)). The eight criminal sexual assault counts arose from conduct that occurred while Dr. Burpo was performing gynecological examinations. Dr. Burpo moved to dismiss the charges, claiming that the legislative scheme which defines the offense, and the medical examination exception to it, make the statute void for vagueness. The circuit court granted Dr. Burpo’s motion to dismiss, declaring the statutory scheme to be unconstitutionally vague as to the class of persons performing gynecologic exams, including this defendant. The State now appeals. (134 Ill. 2d R. 603.) We reverse.
We first address the State’s contention that defendant does not have standing. According to the State, defendant’s arguments are based on hypothetical applications of the statute to punish innocent conduct for which defendant was not charged. Defendant’s mere status as a gynecologist, the State contends, does not confer upon him the standing to challenge the statute on its face where the statute is capable of a valid application to him.
The State’s contention is wrong. The defendant does not contest the constitutionality of the statute as a mere disinterested gynecologist who is concerned about the potential application of the statute. Rather, defendant contests the validity of a statute which has criminalized certain actions he took during several gynecological examinations. The facts of the case against the defendant directly implicate what he claims to be the statute’s constitutional infirmity, that the standards set forth in the statute are unconstitutionally vague as applied to him.
The statute provides that an accused commits criminal sexual assault if he commits an act of sexual penetration and the accused knew that the victim was unable to understand the nature of the act or was unable to give knowing consent. It then sets forth an exception or exemption to the offense of aggravated criminal sexual assault: "Any medical examination or procedure which is conducted by a physician, nurse, medical or hospital personnel, parent, or caretaker for purposes of and in a manner consistent with reasonable medical standards is not an offense ***.” Ill. Rev. Stat. 1991, ch. 38, par. 12 — 18(b).
Long-accepted standards of statutory construction mandate that statutes are entitled to a presumption of constitutionality with the burden of establishing a constitutional violation resting upon the party challenging the statute. Moreover, if construction of a statute is doubtful, the doubt should be decided in favor of the law’s validity. There is a further overriding principle of statutory construction that the court should ascertain and give effect to the intent of the legislature.
At the outset, it is important to establish what the State must prove in prosecuting a gynecologist under the statute. The defendant suggests that a physician commits acts which constitute criminal sexual assault in every gynecological examination he performs. Therefore, the defendant contends, once the physician is indicted for the crime of sexual assault, the burden impermissibly shifts to the physician to establish by a preponderance of the evidence that he is entitled to the statutory medical exemption.
The defendant’s construction of the statute is flawed. Under the statute, the prosecution must prove not only the act of sexual penetration but also that the defendant knew that the patient did not consent. The State contends, and we agree, that there is substantial interplay between the two sections. Specifically, subsumed within the sexual assault statute is the premise that the patient would only consent to an examination which was conducted pursuant to reasonable medical standards. When a gynecologist intentionally exceeds the scope of reasonable medical standards, the patient’s consent is vitiated, and the physician may be prosecuted under the sexual assault statute. Therefore, the burden is on the State to establish beyond a reasonable doubt what the reasonable medical standards were, that the physician intentionally transgressed those standards, and that the patient did not consent to the transgressions.
The defendant’s assertion that mere negligence can subject a gynecologist to prosecution for criminal sexual assault is baseless. The physician’s good faith will protect him from criminal sanctions. In People v. Terrell (1989), 132 Ill. 2d 178, 207, the court found that the legislature eliminated acts of sexual penetration with innocent intentions from the purview of the aggravated criminal sexual assault statute. Consistent with the holding in Terrell, we find that, in prosecuting a gynecologist under the sexual assault statute, the State must prove that the gynecologist possessed a mental state of intent, knowledge, or recklessness.
Thus, gynecologists are not implicated under the sexual assault statute simply because they perform invasive physical examinations. The State bears the burden of proof, and the defendant may attempt to avail himself of the exception by either rebutting the State’s evidence regarding reasonable medical standards, rebutting the State’s evidence concerning his mental state, or rebutting the State’s evidence concerning the patient’s consent.
Since determining the scope of consent in applying the sexual assault statute to gynecologists implicates the reasonable medical standards language in the exception to the statute, we next address the defendant’s contention that the reasonable medical standards language implicated by the sexual assault statute is unconstitutionally vague.
A statute is said to violate due process under either the United States Constitution or the Illinois Constitution on the basis of vagueness only if its terms are so ill-defined that the ultimate decision as to its meaning rests on the opinions and whims of the trier of fact rather than any objective criteria or facts. (People v. Pembrock (1976), 62 Ill. 2d 317, 322.) A statute will be considered unconstitutionally vague on its face only where it is incapable of any valid application in the sense that no standard of conduct is specified at all. (People v. Haywood (1987), 118 Ill. 2d 263, 270, quoting Coates v. City of Cincinnati (1971), 402 U.S. 611, 614, 29 L. Ed. 2d 214, 217, 91 S. Ct. 1686, 1688.) Further, due process requires that a statute must not be so vague that men of common intelligence must necessarily guess at its application or meaning. (People v. Fabing (1991), 143 Ill. 2d 48, 53.) Applying these principles to the present case, we find that the statute is sufficiently clear.
Criminal acts cannot always be defined with absolute precision. Laws criminalizing obscenity, for instance, are framed in general terms. However, they have withstood constitutional scrutiny. (See People v. Ridens (1974), 59 Ill. 2d 362.) Obscenity laws are necessarily flexible because they are based upon community standards which vary from place to place and may change over time.
Similarly, in civil medical malpractice actions, the testimony of experts is needed to establish the applicable standard of care. Medical standards are not amenable to precise and explicit statutory codification. This court has previously observed that medicine is not an exact science. It is rather a profession which involves the exercise of individual judgment within the framework of established procedures. Differences in opinion are consistent with the exercise of due care. Walski v. Tiesenga (1978), 72 Ill. 2d 249, 261.
Therefore, the legislative use of the term "reasonable medical standards” is sufficient. Common sense must play a role in the construction of statutes. As this court observed in Haywood:
"It cannot be presumed that the General Assembly, in legislating, intended obscurity, or 'to override common sense.’ [Citations.] Furthermore, the defendants’ interpretation is inconsistent with established principles of statutory construction. The statute should be given a construction that is consistent with the purposes and policies of the statute.” Haywood, 118 Ill. 2d at 270.
Accordingly, we hold that the statutory scheme under consideration is constitutional. The judgment of the circuit court of St. Clair County dismissing the criminal sexual assault counts against the defendant is therefore reversed. The cause is remanded to the circuit court for further proceedings.
Reversed and remanded.