dissenting:
The majority holds that the trial court erred in refusing to give the jury an informational instruction explaining the consequences of a verdict of not guilty by reason of impaired mental condition. I believe the majority’s opinion is an unnecessary expansion of People v. Thomson, 197 Colo. 232, 591 P.2d 1031 (1979), in which we held that a jury could be given an informational instruction when confronted with the choice of a verdict of sane or not guilty by reason of insanity. Section 18-1-803(3), 8B C.R.S. (1986), on the affirmative defense of impaired mental condition, requires a jury to first determine if the defendant is guilty or not guilty of the charges. A Thomson informational instruction prior to a verdict on the charges should not in my opinion be required. Accordingly, I respectfully dissent.
The defendant was charged with one count of first degree murder, one count of first degree assault, two counts of second degree assault, and one count of committing a crime of violence. After the charges were filed, the deféndant entered a plea of not guilty by reason of insanity. A separate trial was held to determine the issue of the defendant’s sanity. The jury found the defendant legally sane.
The defendant then entered a plea of not guilty by reason of impaired mental condition. At the trial on the merits, the defendant raised the issue of his impaired mental condition through the testimony of his family and a neighbor. The prosecution rebutted this evidence with the testimony of three psychiatrists and a neurologist. At the conclusion of the evidence, the defendant requested that the jury be instructed, at the same time the court was to give instructions on the charges, on the consequences of finding the defendant not guilty by reason of impaired mental condition. The trial court denied this request and stated:
The jury is to determine, first, whether a person is guilty or innocent, and in doing so they are to consider the impaired mental condition as a defense. If and only if they have determined that a person is not guilty, then is an interrogatory given to them as to whether or not the person *75was found not guilty because of impaired mental condition.
The court of appeals affirmed the trial court’s decision. We are asked to determine whether a defendant interposing a defense of impaired mental condition is entitled to an informational instruction explaining the consequences of a verdict of not guilty by reason of impaired mental condition.
I.
The affirmative defense of impaired mental condition permits a defendant to contest the commission of a crime due to an alleged inability to formulate the requisite intent. People v. Low, 732 P.2d 622, 632 (Colo.1987). Under section 18-1-803(1), a defendant may offer evidence of an impaired mental condition to negate “the culpable mental state which is an element of the offense charged.” § 18-1-803(1), 8B C.R.S. (1986).1
The courts, however, are required to follow legislatively mandated procedures in submitting the defense of impaired mental condition to the jury. § 18-1-803(3). First, the trier of fact must decide whether the defendant is guilty or not guilty of any felony charges. Id; see generally People v. Collins, 752 P.2d 93, 98 (Colo.1988) (recognizing the procedure followed under section 18-1-803). Second, if, and only if, a defendant is found not guilty on all felony counts, the jury is required to answer special interrogatories indicating whether the defendant is not guilty by reason of impaired mental condition. § 18-1-803(3); Collins, 752 P.2d at 97-98. See also Sammons, Legislative Update, 12 Colo.Law. 1251, 1252 (1983). The special interrogatories are “to be considered only after the determination concerning guilt ha[s] been made as to each charge.” Collins, 752 P.2d at 98.2
It is important to note that under section 18-1-803(3), the jury is first charged with determining whether the defendant is guilty or not guilty of the charges. If the defendant is found guilty as to one or more felony counts, the defendant is then subject to incarceration with the department of corrections. Collins, 752 P.2d at 97. A finding of guilt’renders the special interrogatories irrelevant because the reasons that the *76defendant was not guilty of the other charges are no longer important once the defendant is subject to incarceration. Id. Thus, the jury does not make a finding of not guilty by reason of impaired mental condition unless and until the jury concludes that the defendant is not guilty on all felony charges.3
II.
Section 18-1-803(3) requires first that the jury make a finding of whether the defendant is guilty or not guilty of the charges. The statute clearly provides that only if the défendant is found not guilty on all felony charges should the court give the special interrogatories to the jury to determine if the defendant was found not guilty by reason of impaired mental condition. It is at that time, after the defendant is found not guilty of all felony charges, that the reasoning in Thomson applies and an informational instruction could be given.
In Thomson, we relied on the reasoning in Lyles v. United States, 254 F.2d 725 (D.C.Cir.1957). In Lyles, the jury had to decide between one of three verdicts: guilty, not guilty, or not guilty by reason of insanity. The court stated that “[¡jurors, in common with people in general, are aware of the meanings of verdicts of guilty and not guilty.... But a verdict of not guilty by reason of insanity has no such commonly understood meaning.” Lyles, 254 F.2d at 728. Because a not guilty by reason of insanity verdict is not commonly understood, the court affirmed an informational instruction to explain the meaning of this verdict to the jury. Id.
In Thomson, the jury had to decide whether the defendant was not guilty by reason of insanity.4 We found the reasoning in Lyles persuasive and stated that “although an average juror understands the consequences of either a guilty or not guilty verdict, the average juror is not aware of the consequences of a verdict of not guilty by reason of insanity.” Thomson, 197 Colo, at 233, 591 P.2d at 1032. We concluded that an informational instruction was needed to clarify any jury confusion as to the meaning of not guilty by reason of insanity. Id. at 233-34, 591 P.2d at 1032. Thus, Thomson allowed an informational instruction only to assist a jury confronted with a possible verdict other than guilty or not guilty. Id.
III.
It is clear from a review of Lyles and Thomson that the decision to allow an informational instruction was predicated on the jury’s need to be informed of the consequences when deciding whether the defendant was sane or criminally insane. In the present case, and under section 18-1-803(3), the Thomson/Lyles situation does not arise unless the jury is required to answer the special interrogatories.5 Prior *77to the special interrogatories, the jury is confronted only with a choice between guilty and not guilty. In Thomson, we reasoned that the average juror understands these two verdicts. Thomson, 197 Colo, at 233, 591 P.2d at 1032.
For these reasons, I disagree with the majority’s unnecessary expansion of the Thomson rule. I therefore dissent.
I am authorized to say that Chief Justice ROVIRA and Justice ERICKSON join in this dissent.. Unlike the court of appeals decision and the majority opinion, this dissent does not rely on the similarities or differences between the defenses of insanity and impaired mental condition. As this dissent indicates, such similarities and differences generally are not relevant to the decision in this case. It should be noted, however, that while the majority stresses the similarities between insanity and impaired mental condition in order to support their opinion, they only touched upon the fact that these two defenses are quite separate and distinct. Insanity is an affirmative defense that “is akin to the common-law plea of 'confession and avoidance,’ and admits the commission of the offense but avoids or provides an excuse for criminal responsibility because the accused was insane at the time of the commission of the offense.” People v. Low, 732 P.2d 622, 629 (Colo.1987).
The defense of impaired mental condition allows the defendant to introduce evidence of an impaired mental condition, § 18-1-803(1), which means a condition of mind, caused by mental disease or defect, which does not constitute insanity. § 16-8-102, 8A C.R.S. (1986). "The sole effect of the defense of impaired mental condition is to negate the existence of an element of the crime charged." Low, 732 P.2d at 631 (Colo.1987). "Thus, unlike the insanity defense, the successful assertion of impaired mental condition negatives the commission of the crime." Id. at 632.
For example, in order for a defendant to be guilty of first degree murder, a defendant must be both sane and have acted willfully, deliberately and with premeditation. The insanity defense applies to the former and the impaired mental condition defense is an element of the latter. The majority's opinion elevates the defense of impaired mental condition to the level of the insanity defense.
. Section 18-1-803(3) provides that "[i]f the trier of fact concludes that guilt has been proven beyond a reasonable doubt as to one or more of the felony charges submitted for consideration, the special interrogatories shall not be answered.”
The possibility exists that the defense of impaired mental condition might result in a complete acquittal of the defendant if there is no lesser offense as to which the defendant possesses the requisite mental state. W. LaFave & A. Scott, Criminal Law § 4.7, at 373 (2d ed.1986). This may result in the release of someone who still poses a threat to society. The legislature required the jury to answer the special interrogatories upon rendering a not guilty verdict to prevent such a release from occurring. See Sammons, Legislative Update, 12 Colo.Law. 1251, 1252 (1983).
. The affirmative defense of impaired mental condition in the trial on the charges is treated as any other affirmative defense (e.g., self-defense, alibi, duress) in that the prosecution has the burden of proving all the elements of the crime charged and disproving the affirmative defense beyond a reasonable doubt. The difference between the defense of impaired mental condition and other affirmative defenses occurs after a verdict of not guilty is entered. As to other affirmative defenses, the defendant is discharged from custody. In the impaired mental condition defense, the jury must answer the special interrogatories so that the court can determine if the defendant is to be discharged or committed to the department of institutions for treatment of a mental condition.
. Under Colorado law, the issue of insanity is tried separately from the trial on the merits to a different jury. § 16-8-104, 8A C.R.S. (1986). At the sanity trial, the jury must decide whether the defendant is sane or not guilty by reason of insanity. § 16-8-105(3), (4), 8A C.R.S. (1986).
.The trial court followed the proper procedure in submitting the defense of impaired mental condition to the jury. The trial court concluded that the jury must first return a verdict as to the fundamental issue of guilty or not guilty and that the special interrogatories would be considered only if the jury returned a verdict of not guilty. Once the jury returned their verdict, the trial court stated that "we will retire ... to chambers and we will then work over the instructions concerning mandatory sentencing counts, if any, and the impaired mental condition special interrogatory or finding, if any.” I agree that under § 18-1-803(3) the jury does not need to consider the special interrogatories unless they return a verdict of not guilty. See People v. Collins, 752 P.2d 93, 98 (Colo.1988).