Reiber, J.
¶ 1. We accepted this interlocutory appeal to consider
whether a defendant charged with murder may assert either the defense of diminished capacity to reduce the offense to manslaughter, or insanity to excuse the offense entirely, where the voluntary use of illegal drugs was an essential causal factor in the defendant’s psychotic state at the time of the offense. Consistent with the law of this and other states, we conclude that a defendant in these circumstances may argue for a reduction of the offense based upon an inability to form the requisite intent to commit murder, but may not be relieved entirely of responsibility for his or her criminal acts. Accordingly, as explained more fully below, we affirm in part, reverse in part, and remand for further proceedings.
¶ 2. Although this appeal is from a pretrial ruling, the material facts are largely undisputed. On the night of September 27, 2000, police found a Japanese exchange student, Atsuko Ikeda, lying in the street in Winooski. Ikeda had suffered serious injuries, and died shortly after transport to the hospital. During the ensuing investigation, defendant walked onto the crime scene and lay down on the street in front of a police cruiser. Upon questioning by the police, defendant reportedly said, “Just cuff me, I know I did something bad, I just don’t know what.” Defendant was charged with Ikeda’s murder.
¶ 3. While in custody, defendant informed the police that, on the day in question, he had killed his cat and then gone outside intending to kill a person. He recalled lunging at a woman passing on a bicycle (later identified as Ikeda) and then beating her repeatedly until she stopped moving. Defendant later told psychiatrists that he had taken a variety of illegal drugs during the six months preceding the incident. Defendant recounted that for about two months, in July and August 2000, he took many “hits” of LSD, and that his last reported use of LSD was two to three weeks before the September killing. Defendant explained that on the night of the incident he felt that he needed to kill people and “gather their souls.”
¶ 4. At defendant’s arraignment on a charge of second-degree murder, the court ordered a psychiatric evaluation of defendant’s [37]*37competency and sanity.2 In December 2000, Dr. Robert Linder, the court-appointed psychiatrist, filed a lengthy report with the court, ultimately concluding that defendant was insane at the time of the offense. The conclusion was based on a series of interviews with defendant and others, defendant’s psychiatric and family history, and a battery of psychological tests from which Dr. Linder inferred that defendant was in a florid psychotic state at the time of the crime that prevented him from appreciating the wrongfulness of his conduct or conforming his conduct to the requirements of law. Dr. Linder’s preliminary diagnosis was that defendant suffered from either a previously undiagnosed mental disease involving a schizophrenic disorder, or a substance-induced psychosis. At a later deposition in 2002, Dr. Linder noted that defendant’s psychotic thoughts had largely resolved and that he had returned to his “usual self,” suggesting a primary diagnosis of schizophrenoform disorder, in which psychotic symptoms last between one to six months.
¶ 5. In his December 2000 report, Dr. Linder indicated that defendant’s mental state had improved over the course of their interviews and that he appeared to be competent to stand trial. Based on the report, the parties stipulated to defendant’s competency, and the court scheduled a hospitalization hearing. Following the hearing, the court found that defendant was a person in need of treatment and ordered him committed to the Vermont State Hospital.
¶ 6. In February 2001, defendant notified the State that he intended to present expert testimony in support of an insanity defense, and the court granted the State’s motion for an independent psychiatric evaluation. In April, the State’s psychiatrist, Dr. Albert Drukteinis, filed a report concurring in Dr. Linder’s opinion that defendant was psychotic at the time of the offense, but concluding that it was caused solely by defendant’s voluntary use of illegal drugs. Although Dr. Drukteinis observed signs of a personality disorder with narcissistic features, he found no evidence that defendant suffered from a major thought disorder such as schizophrenia. At a subsequent hearing on the State’s motion to amend defendant’s conditions of release, defendant’s treating psychiatrist, Dr. Margaret Bolton, also diagnosed defendant as [38]*38having a personality disorder, and agreed that defendant did not suffer from any major mental illness such as schizophrenia, as reported by Dr. Linder, or borderline personality, as suggested in an earlier report by Dr. Bertold Francke. In June 2002, the court transferred custody of defendant to the Department of Corrections after concluding that his continued hospitalization was no longer justified.
¶ 7. In July 2002, the State filed a motion in limine seeking to prevent defendant from presenting an insanity defense at trial, arguing that Vermont law does not recognize temporary insanity caused by the voluntary use of drugs. The State also moved to preclude a diminished capacity defense, asserting that second-degree murder based on wanton disregard for the likelihood that one’s actions would naturally cause death or great bodily harm is a general intent crime to which the defense has no application. After the parties submitted supplemental briefing, the court requested that defendant provide a concise statement of his theory as to the insanity defense. Defendant, in response, submitted a supplemental letter from Dr. Linder, reaffirming his earlier opinion that defendant was in the midst of a severe psychotic episode at the time of the offense, resulting from either a substance-induced psychosis or an underlying mental illness, such as schizophrenoform disorder, caused by the ingestion of illegal drugs in combination with an underlying psychological vulnerability that predisposed him to such a reaction.
¶ 8. In March 2003, the court issued a written decision, concluding that second-degree murder based on wanton disregard of the likelihood that one’s conduct would naturally cause death or great bodily harm is a specific intent crime in Vermont. Therefore, it held that defendant was entitled to rely on the defense of diminished capacity due to voluntary intoxication. The following June, the court issued a second decision, concluding that defendant was also entitled to argue that he was legally insane at the time of the killing. Although the court ruled that “an individual whose mental state is altered solely because of the consumption and abuse of illegal drugs” may not assert an insanity defense, it found that one whose consumption of illegal drugs activates a latent mental disease or defect resulting in a psychotic reaction is entitled to a complete defense to the crime charged, unless the defendant knew or had reason to know that the drugs would elicit such a reaction.
¶ 9. The State moved for permission to pursue an interlocutory appeal of both orders. The trial court granted the motions, certifying the following three questions, which we accepted for review:
[39]*39(1) Does the issue of diminished capacity caused by voluntary intoxication by means of illegal drugs apply to a charge of second degree murder based upon wanton disregard of the likelihood that one’s conduct would naturally cause death or great bodily harm, so as to reduce the offense to voluntary manslaughter?
(2) Does the issue of diminished capacity caused by a combination of pre-existing mental condition and the effects of voluntary consumption of illegal drugs apply to a charge of second degree murder based upon wanton disregard of the likelihood that one’s conduct would naturally cause death or great bodily harm, so as to reduce the offense to voluntary manslaughter?
(3) Is the following a correct statement of Vermont law:
The term “mental disease or defect” as used in 13 V.S.A. § 4801 includes a mental condition caused by the voluntary consumption of illegal drugs if the drugs activate a latent mental disease or defect, and as a result of that mental disease or defect the individual has lost the capacity to appreciate the criminality of his conduct, or has lost the capacity to conform his conduct to the requirements of the law, unless the individual knew or had reason to know that the drug would activate the illness. The resulting disease or defect must be recognized medically and must exist at the time of the offense, independent of any temporary intoxication or high that the drugs caused. It does not matter that the mental disease or defect was not permanent, if the condition lasted for a substantial time after the intoxicating effects of the illegal drugs had worn off. A mental disease or defect cannot be caused solely by the consumption of an illegal drug.
I.
¶ 10. This interlocutory appeal presents questions of law, and our review is therefore nondeferential and plenary. State v. Koch, 169 Vt. 109, 112, 730 A.2d 577, 580 (1999).
[40]*40¶ 11. The first two certified questions ask us to reexamine the common law of diminished capacity. The State suggests that our recent decisions have made such a defense unavailable to a defendant charged with second-degree murder based on a wanton disregard of the likelihood that the defendant’s conduct would naturally cause death or great bodily harm. We disagree, and affirm the district court’s ruling.
¶ 12. Title IB V.S.A. § 2301 defines the degrees of murder as follows:
Murder committed by means of poison, or by lying in wait, or by wilful, deliberate and premeditated killing, or committed in perpetrating or attempting to perpetrate arson, sexual assault, aggravated sexual assault, robbery or burglary, shall be murder in the first degree. All other kinds of murder shall be murder in the second degree.
This skeletal statutory definition has existed largely unchanged since 1869, and the Legislature has left it to this Court to flesh out the elements of second-degree murder. State v. Johnson, 158 Vt. 508, 517, 615 A.2d 132, 137 (1992). We have distinguished between first- and second-degree murder based on the presence or absence of “willfulness, deliberation and premeditation,” State v. Hatcher, 167 Vt. 338, 343, 706 A.2d 429, 432 (1997), but have traditionally held that a person must act with “malice” to be guilty of either degree of murder. State v. Long, 95 Vt. 485, 496, 115 A. 734, 739 (1922). Our more recent decisions have concluded that the term “malice” is overly confusing, however, and we have directed the trial courts to instruct jurors on the specific mental states requisite to a particular charge. See, e.g., Johnson, 158 Vt. at 519, 615 A.2d at 138. To this end, we have reiterated that the crime of second-degree murder requires “‘an intention to kill, an intention to do great bodily harm, or a wanton disregard of the likelihood that one’s behavior may naturally cause death or great bodily, harm.’” Hatcher, 167 Vt. at 344, 706 A.2d at 433 (quoting State v. Doucette, 143 Vt. 573, 582, 470 A.2d 676, 682 (1983)).
¶ 13. We have long held that diminished capacity due either to voluntary intoxication, In re Plante, 171 Vt. 310, 317, 762 A.2d 873, 878 (2000), or to a mental disability, State v. Wheelock, 158 Vt. 302, 311, 609 A.2d 972, 978 (1992), can mitigate murder to voluntary manslaughter. The traditional rationale supporting a diminished capacity defense posits that a defendant’s decreased faculties or awareness may preclude the specific intent to commit murder, thus reducing the crime [41]*41to voluntary manslaughter. State v. Pelican, 160 Vt. 536, 539, 632 A.2d 24, 26 (1993). In State v. Blish, 172 Vt. 265, 272, 776 A.2d 380, 386 (2001), however, we announced that “the intent component of voluntary manslaughter is the same as that required for second degree murder.” We went on to state that the “critical factor distinguishing second degree murder from voluntary manslaughter is not the mental state of the actor, but the existence of mitigating circumstances.” Id. Thus, we adopted the position that “‘the correct way of explaining [diminished capacity] is as a defense mitigating the degree of homicide from murder to voluntary manslaughter.’” Id. at 270, 776 A.2d at 385 (quoting Pelican, 160 Vt. at 543, 632 A.2d at 29 (Morse, J., concurring)).
¶ 14. The State argues that our efforts to modernize the language of homicide have actually created two distinct classifications of second-degree murder: the first applicable to a defendant who intended to kill his victim, and the second applicable to a defendant who acted with wanton disregard for the consequences of his or her actions. The State contends that second-degree murder based on “wanton disregard” is actually a general intent crime, to which the diminished capacity defense has no application. We are not persuaded. As discussed above, second-degree murder requires either an intent to kill or do great bodily harm, or “a wanton disregard of the likelihood that one’s behavior may naturally cause death or great bodily harm.” Hatcher, 167 Vt. at 344, 706 A.2d at 433 (quotations omitted). Although we originally presented this tripartite definition as an explication of the elusive term “malice,” which has long been the distinct mens rea — the specific intent — separating murder from manslaughter, Doucette, 143 Vt. at 582, 470 A.2d at 682, the State now contends that “wanton disregard” actually denotes a subset of recklessness, or general intent. Despite the historical connection between the term “wanton” and the term “malice,”3 the State contends that a combined reading of several recent decisions indicates that we now consider “wanton disregard” a species of general intent.
¶ 15. The first step in the State’s argument relies on our recent observation that the phrase “wanton disregard” describes a mental state equivalent to “extreme indifference.” Blish, 172 Vt. at 272-73, 776 [42]*42A.2d at 386. The State next points out that we have held that diminished capacity due to voluntary intoxication is no defense to a charge of aggravated assault when the defendant is accused of acting recklessly “under circumstances manifesting extreme indifference to the value of human life.” State v. Allen, 169 Vt. 615, 616, 738 A.2d 113, 114 (1999) (mem.) (citing 13 V.S.A. § 1024(a)(1)) (emphasis added). In these two steps, then, the State contends that “wanton disregard” is equivalent to “extreme indifference,” which, in turn, is a species of recklessness to which the diminished capacity defense does not apply. At the very least, the State argues that Allen creates an unexplained split in the law of “extreme indifference,” whereby diminished capacity due to voluntary intoxication applies to murder, but not to some types of aggravated assault.
¶ 16. The reason for this split, however, is that the Legislature has acted to modernize the statutory language defining aggravated assault, while it has chosen to leave the common-law definition of second-degree murder undisturbed. Compare 13 V.S.A. § 1024(a)(1) (amended in 1972) with 13 V.S.A. § 2301 (substantially unchanged since 1869). The mental state defined in § 1024(a)(1) • — ■ “purposely, knowingly or recklessly under circumstances manifesting extreme indifference to the value of human life” — closely reflects the terminology of the Model Penal Code. Model Penal Code § 2.02(2) (1985); see also State v. Trombley, 174 Vt. 459, 461, 807 A.2d 400, 404 (2002) (mem.) (interpreting § 1024 pursuant to the Model Penal Code). The Model Code moves away from the old distinction between specific and general intent, and does not recognize intoxication as a defense to crimes that require only a showing of recklessness. Model Penal Code §2.08(2). Because the assault language in our statute closely mirrors the Code, we essentially adopted the Code’s position on diminished capacity. Acknowledging the three separate mental states delineated in the statute, we concluded that diminished capacity would apply to assaults committed purposely or knowingly, but held that the dejfense of voluntary intoxication is not available when a defendant acts recklessly. Allen, 169 Vt. at 616, 738 A.2d at 114.
¶ 17. The Legislature has not modernized the statutory definition of second-degree murder, however, which remains a creature of the common law, and therefore is subject to the traditional distinction between specific and general intent. The common law allows the defense of diminished capacity — due either to intoxication or mental defect — to specific intent crimes, and we have consistently made the defense available to negate the specific intent necessary to commit [43]*43second-degree murder. State v. Shaw, 168 Vt. 412, 416, 721 A.2d 486, 490 (1998). All three prongs of the mens rea required for second-degree murder — intent to kill, intent to cause great bodily harm, or wanton disregard of the likelihood that one’s conduct would naturally cause death or great bodily harm — simply define the term “malice,” Doucette, 143 Vt. at 582, 470 A.2d at 682, which has always been a species of specific intent. The State’s arguments are therefore unavailing, and defendant is entitled to present evidence that his diminished capacity, due either to voluntary intoxication or mental disability, prevented him from forming the specific intent to commit second-degree murder.4
II.
¶ 18. The final certified question asks us to determine whether defendant can present an insanity defense based on his claim that the ingestion of illegal drugs activated a latent mental disease or defect resulting in a psychotic reaction that rendered him unable to appreciate the criminality of his conduct or conform his conduct to the requirements of law.
¶ 19. Unlike diminished capacity, which mitigates a defendant’s culpability, legal insanity is a complete defense to any crime. State v. Messier, 145 Vt. 622, 628, 497 A.2d 740, 743 (1985). The insanity defense has a long history at common law. See B. Elkins, Idaho’s Repeal of the Insanity Defense: What Are We Trying to Prove?, 31 Idaho L. Rev. 151, 161 (1994) (discussing the historical roots of the insanity defense). The modern standard dates to the early nineteenth-century House of Lords’ decision in M’Naghten’s Case, 8 Eng. Rep. 718, 722 (H.L. 1843), which looked to whether the defendant knew the nature or quality of his actions, or understood that they were wrong. The standard has since evolved through a variety of permutations, including the so-called Durham test, from Durham v. United States, 214 F.2d 862 (D.C. Cir. 1954), which asked whether the defendant’s [44]*44crime “was the product of mental disease or mental defect,” id. at 875, which in turn influenced the insanity standard set forth in the Model Penal Code § 4.01. The latter forms the governing standard in most of the federal circuits and roughly half the states, including Vermont. Id. § 4.01, cmt. at 175-76. Our definition is set forth in 13 V.S.A. § 4801(a)(1), as follows:
A person is not responsible for criminal conduct if at the time of such conduct as a result of mental disease or defect he lacks adequate capacity either to appreciate the criminality of his conduct or to conform his conduct to the requirements of law.
¶ 20. Although a separate section of the Model Penal Code provides that “[ijntoxication does not, in itself, constitute mental disease within the meaning of Section 4.01 [the insanity section],” Model Penal Code §2.08(3), we have not adopted this provision in Vermont, and our insanity statute does not define “mental disease or defect” other than to exclude “an abnormality manifested only by repeated criminal or otherwise anti-social conduct,” and to include “congenital and traumatic mental conditions as well as disease.” 13 V.S.A. § 4801(a)(2). Nevertheless, we have long held that, while voluntary intoxication may mitigate the crime charged, it will not operate as a total bar to criminal responsibility. Wheelock, 158 Vt. at 309, 609 A.2d at 976. This is the rule nationally as well. See P. Hassman, Annotation, Effect of Voluntary Drug Intoxication Upon Criminal Responsibility, 73 A.L.R.3d 98, 121 (1976) (“[I]t is generally accepted that voluntary drug intoxication may not be used to completely excuse one from criminal responsibility.”).
¶ 21. While the mental state resulting from extreme intoxication may in some cases be “tantamount to insanity,” L. Tiffany, The Drunk, the Insane, and the Criminal Courts: Deciding What to Make of Self-Induced Insanity, 69 Wash. U. L.Q. 221, 222 (1991), its origin as a self-induced impairment fundamentally distinguishes it for most courts from a naturally occurring mental disease or defect that leads to insanity. See J. Dressier, Understanding Criminal Law § 24.05[A], at 328-29 (3d ed. 2001). Indeed, it is universally recognized that a condition of insanity brought about by an individual’s voluntary use of alcohol or drugs will not relieve the actor of criminal responsibility for his or her acts. See W. LaFave, Criminal Law § 9.5(h), at 481-82 (4th ed. 2003).
[45]*45¶ 22. The only generally recognized exception to this rule is the doctrine known as “fixed” or “settled” insanity.5 Nearly every court and commentator that has addressed this doctrine has defined it as a permanent or chronic mental disorder caused by the habitual and long-term abuse of drugs or alcohol. See, e.g., A. Levine, Note, Denying the Settled Insanity Defense: Another Necessary Step in Dealing with Drug and Alcohol Abuse, 78 B.U. L. Rev. 75, 78 (1998) (“The long-term, consistent abuse of drugs or alcohol may result in permanent mental disorders that are symptomatically and organically similar to mental disorders caused by brain disease. Courts have labeled this condition as ‘fixed’ or ‘settled’ insanity, because the disorder remains even though the defendant is not under the influence of the intoxicants.”); Tiffany, supra, at 225 (“the courts will recognize even a Voluntarily contracted madness’ as insanity if it has become permanent as in the case of ‘fixed’ or ‘settled’ insanity, even though it has its origins in alcohol or other drug abuse”); J. Dressier, supra, § 24.05[B], at 329 (“Habitual use of intoxicants can result in permanent brain damage, resulting in a substance-induced mental disorder that persists, i.e., the disorder remains even when the actor is not under the influence of intoxicants.”); People v. Whitehead, 525 N.E.2d 1084, 1087 (Ill. App. Ct. 1988) (insanity defense resulting from drug use is not available “absent a mental defect or disease traceable to chronic or habitual drug use and resulting in a permanent kind of insanity”); see generally R.W. Gascoyne, Annotation, Modem Status of the Rules as to Voluntary Intoxication as Defense to Criminal Charge, 8 A.L.R.3d 1236 (1966) (collecting cases).
¶ 23. Scholars have traced the origins of the settled insanity defense in this country to the mid-nineteenth century when courts first considered the culpability of chronic alcoholics for crimes committed in the throes of acute alcohol-induced psychoses, typically marked by hallucinations and paranoid delusions. See generally Levine, supra, at 87 (noting that “[a] Tennessee state court first recognized the rarely invoked doctrine of settled insanity in 1850”); Note, Intoxication as a Criminal Defense, 55 Colum. L. Rev. 1210, 1219 n.66 (1955) (citing [46]*46early decisions that recognized settled insanity defense in cases of “delirium tremens ... a phenomenon brought about by alcoholic abuse over many years — 6 to 10 years of heavy drinking”); Am. Psychiatric Ass’n, Diagnostic and Statistical Manual of Mental Disorders 153 (4th ed. 1994) (observing that “Substance-Induced Persisting Dementia” generally originates from “a pattern of prolonged and heavy substance use” with symptoms that “persist long after use of the substance has stopped,” and is generally characterized by “an insidious onset and slow progression” so that it is “rarely” seen in persons under 20).6
¶ 24. From its inception to the present, the settled insanity doctrine has been consistently characterized as a state of mind resulting from “long-continued,” “habitual,” “prolonged,” or “chronic” alcohol or drug abuse leading to a more or less permanent or “fixed” state of insanity. For an illustrative sample of older decisions, see, e.g., People v. Travers, 26 P. 88, 91 (Cal. 1891) (“[SJettled insanity produced by a long-continued intoxication, affects responsibility in the same way as insanity produced by any other cause.”); Fisher v. State, 64 Ind. 435, 440 (1878) (recognizing settled insanity defense “where the habit of intoxication, though voluntary, has been long continued, and has produced disease, which has perverted or destroyed the mental faculties of the accused”); State v. Riley, 13 S.W. 1063, 1064 (Mo. 1890) (holding that “long-continued habits of intemperance, producing permanent mental disease amounting to insanity” may relieve defendant of criminal responsibility); Cheadle v. State, 149 P. 919, 922 (Okla. Crim. App. 1915) (recognizing settled insanity due to “excessive and [47]*47long-continued indulgence in alcoholic liquors, technically called, ‘delirium tremens’”); State v. Kidwell, 59 S.E. 494, 495 (W. Va. 1907) (recognizing defense of settled insanity “superinduced by habitual and long continued intoxication”). For more recent cases illustrating the same principle, see, e.g., Evans v. State, 645 P.2d 155, 158 (Alaska 1982) (recognizing insanity defense for “alcoholic psychosis such as delirium tremens, resulting from long-continued habits of excessive drinking”); Kiley v. State, 860 So. 2d 509, 511 n.3 (Fla. Dist. Ct. App. 2003) (“[T]he defendant must show that his long term, and continued use of intoxicants produced a fixed and settled frenzy or insanity either permanent or intermittent.”) (quotation omitted); State v. Clokey, 364 P.2d 159, 164 (Idaho 1961) (upholding instruction defining settled insanity as “produced by long continued intoxication”); State v. Smith, 490 P.2d 1262, 1264 (Or. 1971) (recognizing insanity defense where “excessive and long-continued use of intoxicants produces a mental condition of insanity, permanent or intermittent”) (quotations omitted); Herbin v. Commonwealth, 503 S.E.2d 226, 231 (Va. Ct. App. 1998) (recognizing settled insanity resulting from “long-term and severe drug abuse”).
¶ 25. The underlying rationale for the settled insanity doctrine is generally explained as an acknowledgment of “the futility of punishment, since the defective mental state is permanent,” Tiffany, supra, at 225 n.16, or, more commonly, as a compassionate concession that at some point a person’s earlier voluntary decisions become so temporally and “morally remote” that the cause of the offense can reasonably be ascribed to the resulting insanity rather than the use of intoxicants. Dressler, supra, § 24.05[B], at 330; see also Note, Settled Insanity is Not a Defense: Has the Colorado Supreme Court Gone Crazy? Bieber v. People, 43 U. Kan. L. Rev. 259, 270 (1994) (“Proponents of a settled insanity defense believe the initial choice to use drugs to be too remote in time to hold a person accountable for it once that person eventually suffers a drug-induced brain disorder.”). As the celebrated American jurist and scholar Joseph Story, in one of the earliest reported cases on the subject, observed: “[T]he question made at the bar is, whether insanity, whose remote cause is habitual drunkenness, is, or is not, an excuse in a court of law for a homicide committed by the party, while so insane, but not at the time intoxicated or under the influence of liquor.” United States v. Drew, 25 F. Cas. 913 (D. Mass. 1828) (No. 14,993) (emphasis added); see also State v. Stark, 32 S.C.L. (1 Strob.) 479 (S.C. Ct. App. 1847) (acknowledging that insanity defense may lie where de[48]*48fendant’s alcoholic psychosis was “a remote consequence superinduced by the antecedent exhaustion of the party arising from gross and habitual drunkenness”).7
¶ 26. Although, with one exception, every state court to consider the issue has recognized the doctrine of settled insanity, many states — including Vermont — have simply not addressed it. See Levine, supra, at 87-88 (noting that twenty-nine states have recognized settled insanity while twenty have not addressed it); cf. Bieber, 856 P.2d at 817 (rejecting settled insanity as an unprincipled departure from the general rule precluding the insanity defense where defendant’s psychotic state results from voluntary intoxication).8 Defendant tenders this as an appropriate case in which to recognize the doctrine, noting its general acceptance in other states, longevity under the common law, and recognition by the drafters of the Model Penal Code.9
[49]*49¶ 27. We are not persuaded, however, that this appeal presents a suitable factual setting for resolution of the issue. The many cases and articles that consistently require a showing that defendant’s mental illness resulted from “long-term,” “habitual,” or “chronic” drug or alcohol abuse do not, of course, establish any specific time frames relative to the offense, nor is it possible to do so. Yet, by any measure, the circumstances here do not begin to approach the prolonged abuse leading to a fixed insanity that the common law recognized as sufficiently attenuated to excuse, the crime. Whatever its merits, the doctrine of settled insanity was developed to address mental illness resulting from long-term substance abuse over many years, gradually leading to organic brain damage, and its justification is based on the humane recognition “that at some point a person’s earlier voluntary decisions become morally remote.” J. Dressler, supra, § 24.05[B], at 330.
¶ 28. By his own admission, defendant’s LSD use here began in July 2000, lasted about two months, and ended two to three weeks before the offense in late September 2000. He took the drugs precisely to experience the perceptual distortions that may result from such hallucinogens, and fully expected that the drugs would alter his state of mind.10 Although he continued to have bizarre thoughts weeks and months after the offense, he was found to have returned to mental competence to speak with the police and stand trial for his offenses within weeks, if not days, after the murder.11
[50]*50¶29. In these circumstances, the claim that defendant was operating under a “fixed or settled” insanity at the time of the offense is contrary to the very meaning of the doctrine and its altruistic origins. To retain any moral or legal salience, the doctrine must — if it is ever justified ■— be limited to those cases where the initial choice to abuse alcohol or drugs has become so attenuated over time that it serves little or no purpose to hold the defendant accountable for that choice once a permanent mental illness has taken hold through years of chronic substance abuse. To apply the doctrine here, to a crime committed while defendant was either directly under the influence or in the immediate aftermath of a discrete two-month period of using hallucinogenic drugs, would defeat the doctrine’s meaning and underlying purposes. See Allen v. State, 539 So. 2d 1124, 1126 (Ala. Crim. App. 1988) (although defendant had been treated for alcohol abuse on two occasions prior to offense, court held that defendant had “produced no evidence that his long-continued alcohol indulgence had resulted in a mental disease or defect”); State v. Valenzuela, 559 P.2d 201, 204 (Ariz. Ct. App. 1977) (upholding trial court’s refusal to instruct on settled insanity where there was “no evidence to support a finding that the appellant was suffering from an existing state of mental illness caused by prolonged use of liquor”); People v. Free, 447 N.E.2d 218, 232 (Ill. 1983) (upholding court’s refusal to instruct on settled insanity where there was “no evidence in the record that this defendant was a habitual or chronic user of drugs or alcohol, or that the claimed disease or defect was ‘settled’ or ‘fixed’”). While there may indeed be cases that raise a genuine factual issue as to whether a defendant’s prior, long-term drug or alcohol abuse has resulted in a fixed insanity, this is not such a case.12
[51]*51¶ 30. Our conclusion applies with equal force to the alternative settled-insanity theory advanced by the trial court in the proposed instruction at issue here. As noted, Dr. Linder offered two possible diagnoses of defendant’s psychosis at the time of the offense. The first posited that it was a straight substance-induced psychosis, based on his testimony that LSD may continue to affect the user weeks after its last ingestion. The second was that the LSD triggered a latent mental disease or defect, causing the psychotic episode.13 The latter diagnosis differs somewhat from the classic etiology of settled insanity because the theory is not that the illegal drugs caused the illness and resulting [52]*52psychosis, but rather that they exacerbated or activated a preexisting latent illness.
¶ 31. Accepting this theory as a plausible basis for the insanity defense, the trial court crafted an instruction that attempted to articulate its essential elements. Borrowing from a Massachusetts decision, Commonwealth v. Herd, 604 N.E.2d 1294, 1298 (Mass. 1992), the proposed instruction provides that an insanity defense may be predicated upon a mental condition “caused by the voluntary consumption of illegal drugs if the drugs activate a latent mental disease or defect,” provided that the defendant did not know or have reason to know the drug would activate the illness; that the resulting disease is recognized medically and existed at the time of the offense “independent of any temporary intoxication or high that the drugs caused”; and that the mental disease “lasted for a substantial time after the drugs had worn off.” The instruction went on to reject settled insanity in its traditional form, stating that “[a] mental disease or defect cannot be caused solely by the consumption of an illegal drug.”
¶ 32. Although the Herd case actually involved facts closer to a true settled-insanity claim (the evidence showed that the “mental disease or defect [was] caused solely by the consumption of a drug,” id. at 1299), it relied on two earlier decisions, Commonwealth v. Shelley, 409 N.E.2d 732, 738-39 (Mass. 1980), and Commonwealth v. Brennan, 504 N.E.2d 612, 616 (Mass. 1987), which held that a defendant may be entitled to show a lack of criminal responsibility where illegal drugs or alcohol activate a latent disease or defect, resulting in a psychotic episode. Defendant has not shown, nor have we discovered, any significant movement by jurisdictions outside of Massachusetts to apply the Herd formula.
¶ 33. The proposed instruction essentially posits that when the voluntary use of illegal drugs activates a “latent” mental illness resulting in psychosis, we should ignore the fact that illegal drugs were the precipitating cause. This conclusion runs counter to the fundamental principle that a defendant is not excused from criminal liability for acts which result from a mental state that is self-induced through the voluntary ingestion of illegal drugs or alcohol. If defendant here suffered, as Dr. Linder asserts, from a latent mental illness, it does not alter the fact that, as Dr. Linder also explained, defendant would not have been in a psychotic state at the time of the offense had he not [53]*53chosen to use illegal consciousness-altering drugs.14 Thus, the very evidence on which defendant relies defeats his claim, for it demonstrates that his recent, voluntary use of illegal drugs was an essential causal element of the mental illness and psychotic episode that followed. On these facts, defendant was not entitled to assert an insanity defense. See, e.g., Commonwealth v. Henry, 569 A.2d 929, 935 (Pa. 1990) (rejecting defendant’s claim that the trial court erred in precluding an insanity defense based on his theory that he suffered from “an inherent pathologic illness triggered by the voluntary ingestion of alcohol”); Evilsizer v. State, 487 S.W.2d 113, 115 (Tex. Crim. App. 1972) (rejecting proposed instruction that would have allowed finding of insanity where “the accused is in any degree mentally impaired or infirm, and such impairment or infirm condition of his mind was stimulated or aggravated by the use of intoxicants to such an extent as to cause the accused to become temporarily insane”).
¶ 34. Our conclusion is not altered by the instruction’s additional requirement that defendant neither “knew nor had reason to know that the drug would activate the illness.” As we have seen, it is a fundamental tenet of our criminal code that a defendant must be held accountable for the consequences of his or her actions resulting from the voluntary ingestion of illegal drugs or alcohol, and this rule remains unaffected by the possibility that the substance will activate an unknown condition leading to an unexpected reaction. See, e.g., State v. Sette, 611 A.2d 1129, 1136 (N.J. Super. Ct. App. Div. 1992) (rejecting defendant’s claim that he lacked criminal responsibility where his drug use interacted with the unknown presence in his system of agricultural pesticides, resulting in a psychotic reaction “wholly out of line with his reasonable expectations”). Indeed, many courts have held that a defendant can not reasonably assume the use of illegal drugs will have any predictable [54]*54effect. See, e.g., People v. Velez, 221 Cal. Rptr. 631, 638 (Ct. App. 1985) (rejecting claim that defendant was not responsible for his actions after smoking marijuana cigarette unaware that it was laced with PCP since he could not “assume” that the marijuana would “produce any predictable intoxicating effect”); State v. Hall, 214 N.W.2d 205, 208 (Iowa 1974) (holding that defendant could not avail himself of involuntary intoxication defense where he claimed ignorance that the pill he took was LSD but otherwise “knew it was a mind-affecting drug”); Commonwealth v. Campbell, 284 A.2d 798, 801 (Pa. 1971) (observing that the “nonpredictability” of hallucinogenic drugs such as LSD militates against recognizing a defense based on the psychotic state of mind which they induce).15
¶ 35. In response to the third question, therefore, we hold that the proposed instruction did not set forth a correct statement of the insanity defense under 13 V.S.A. § 4801. We recognize that mental disease and the abuse of illegal drugs often coexist, and emphasize that nothing in our holding bars an insanity defense where the prior use of drugs is not an essential causal element of defendant’s mental state. Indeed, nothing that we have said would preclude this or any other defendant from attempting to prove at trial that the alleged insanity at the time of the offense was caused by a mental disease or defect that rendered them incapable of appreciating the criminality of their acts or of conforming their conduct to the requirements of law. Upon such a showing, however, the State may offer evidence to prove that the voluntary ingestion of intoxicants was an essential causal element of the insanity so as to refute the claim that the insanity absolves the defendant of criminal responsibility. See State v. Hanson, 529 A.2d 720, 724 (Conn. App. Ct. 1987) (where defendant has claimed affirmative defense of insanity, “[t]he state may offer evidence that intoxicating liquor was voluntarily ingested so as to cause the disease or defect, to refute the evidence that insanity absolves the defendant of criminal responsibility”).
[55]*55¶ 36. Finally, we note that defendant has not asserted a constitutional right to an insanity defense based on the theory that we have rejected today, and we are reluctant to delve at length into a subject that was not raised below or briefed and argued on appeal. As there is little point, however, to issuing a decision of doubtful constitutional validity, we pause long enough to note the following: The United States Supreme Court has held that there is no due process right to assert a defense of voluntary intoxication so as to mitigate or excuse a charge of murder, Montana v. Egelhoff, 518 U.S. 37, 56 (1996) (Scalia, J., plurality opinion), and we are confident, in light of this holding, that the Court would not find a fundamental right to assert a complete defense based on the voluntary consumption of illegal drugs. Indeed, the high court has traditionally reserved to the states the task of balancing the “constantly shifting ... religious, moral, philosophical, and medical views” that underlie the insanity defense, Powell v. Texas, 392 U.S. 514, 536 (1968), and has expressly “not said that the Constitution requires the States to recognize the insanity defense.” Medina v. California, 505 U.S. 437, 449 (1992). Four state courts have thus upheld legislation virtually abolishing insanity as a defense and allowing evidence of mental disease or defect solely to rebut the mens rea element of the charge. See State v. Searcy, 798 P.2d 914, 919 (Idaho 1990); State v. Bethel, 66 P.3d 840, 851-52 (Kan. 2003); State v. Korell, 690 P.2d 992, 998-1000 (Mont. 1984); State v. Herrera, 895 P.2d 359, 366 (Utah 1995). Therefore, while we need not consider the constitutional dimensions — if any — of our decision, we issue it secure in the understanding that it violates no fundamental rights of defendant.
¶ 37. Our dissenting colleague rather strenuously asserts six purported deficiencies in today’s decision. We address them in order. First, it is asserted that we improperly characterize the case as turning on “intoxication” rather than “accept the reality” that it involves insanity. Post, ¶ 47. On the contrary, the reality here is that defendant has asserted a defense premised on the proposition that his voluntary use of hallucinogenic drugs within weeks of the offense may entirely excuse his actions. While defendant may not have been in the immediate throes of an hallucinogenic “high,” the proximity and short-term nature of his drug use certainly bars any legitimate claim to a settled insanity defense.
¶ 38. Next, the dissent claims that the Court’s decision fails to answer the actual question posed, and instead holds that “defendant should not be able to raise an insanity defense under any circum[56]*56stances.” Post, ¶ 49. We do not believe that anyone reading today’s decision will be left uncertain as to the Court’s answer to the specific question certified for review. As stated earlier, in response to that question, we hold that defendant may not assert an insanity defense premised on the voluntary use of illegal drugs that triggers a latent mental disease or defect.
¶ 39. As to the dissent’s charge that today’s decision precludes defendant from raising an insanity defense “under any circumstances,” even a cursory review of the opinion demonstrates otherwise. The argument appears to be premised on dissatisfaction with the rule barring a claim of insanity if it would not have occurred “but for” the defendant’s voluntary use of illegal drugs. The dissent claims that this will unfairly prevent many mentally ill persons from presenting a legitimate insanity defense. We discern no basis for such a claim, however, and the dissent offers none. “But for” causation is a familiar legal standard that other jurisdictions have utilized in this context. See, e.g., United States v. Henderson, 680 F.2d 659, 662 (9th Cir. 1982) (noting that insanity defense resulting from combination of mental defect and alcohol is unavailable where “absent the alcohol [the] mental defect would not have rendered [the defendant] insane”); Hanson, 529 A.2d at 723 (upholding trial court’s rejection of insanity defense where evidence did not establish “that it was the defendant’s mental condition, absent the ingestion of alcohol, which was the cause of his criminal behavior”); State v. Flagg, No. 9804019233, 1999 WL 167775, at *2 (Del. Super. Ct. March 10, 1999) (interpreting state statute to hold that where alleged insanity “would not have occurred but for such [drug] consumption,... defendant could not present an insanity defense”); see also Conn. Gen. Stat. § 53a-13(b) (2001) (“It shall not be a defense under this section if such mental disease or defect was proximately caused by the voluntary ingestion, inhalation or injection of intoxicating liquor or any drug or substance____”); Del. Code Ann., tit. 11, § 401(c) (2001) (“It shall not be a defense ... if the alleged insanity or mental illness was proximately caused by the voluntary ingestion, inhalation or injection of intoxicating liquor, any drug or other mentally debilitating substance____”); Wash. Rev. Code § 10.77.030(3) (2002) (“No condition of mind proximately induced by the voluntary act of a person charged with a crime shall constitute insanity”). The “but for” standard most effectively advances the underlying principle that a person who would not have been insane at the time of the offense but for the use of illegal drugs should not be excused of responsibility for the crime. As we have emphasized, however, nothing in our decision forecloses defendants [57]*57from claiming or demonstrating that, apart from any incidental drug use, they suffered from a mental disease or defect that rendered them incapable of appreciating the criminality of their acts or conforming their conduct to the requirements of the law.
¶ 40. Next, the dissent claims that the Court has “ignored” the relevant standard of review and “selectively” found facts to support its decision. Post, ¶ 51. On the contrary, the material facts underlying today’s decision are virtually undisputed, and consist entirely of the evidence advanced by defendant (not the State or this Court) in support of his claim. Defendant claims, without dispute, that he consumed large quantities of LSD for about two months during the summer preceding the offense, and stopped about two to three weeks before the attack in September 2000. Assuming these facts to be true, we hold plainly and simply that they are legally insufficient to support a claim of insanity. See State v. Cram, 157 Vt. 466, 469, 600 A.2d 733, 734 (1991) (where the facts asserted by defendant, taken as true, are insufficient to sustain the purported defense, the trial court should deny use of the defense).
¶ 41. The dissent’s recurring claim that the Court ignores or prejudges the record evidence is unfounded. We are well aware of the record evidence of defendant’s troubled family history, of the possibility that defendant suffered from some mental illness prior to the assault of the victim in this case, and of the potential that he may experience cyclical periods of mental illness in the future. As we have stated, defendant is not barred from asserting an insanity defense on this basis. He is barred, however, from claiming a mental illness triggered by the use of illegal drugs.16
¶ 42. Next, the dissent claims that our holding is unprecedented in its restrictions on the insanity defense, contrary to the common law, and constitutes an unwarranted intrusion on the prerogatives of the Legislature. Nothing could be further from the truth. Indeed, as we have seen, to recognize a settled insanity defense in this case would represent a distinct departure from the basic common-law doctrine requiring a fixed mental infirmity resulting from chronic substance abuse over the course of many years. As for the variant set forth in the [58]*58trial court’s proposed instruction, which the dissent has aptly labeled the “Massachusetts defense,” post, ¶ 87, we are aware of no widespread endorsement of this approach. With respect to the dissent’s claim that our holding impermissibly amends the insanity statute, which contains no express exception for insanity caused by drugs or alcohol, we would point out that the argument is fundamentally self-defeating; it acknowledges that in the absence of an express statutory provision, the common law controls. See State v. Francis, 151 Vt. 296, 305, 561 A.2d 392, 397 (1989) (“[T]he common law controls unless modified by statute or case law.”) (quotations omitted). As we have seen, it is well settled that, absent a fixed insanity developed over a prolonged period of abuse, the voluntary use of drugs or alcohol that triggers a psychotic reaction will not absolve a defendant of criminal responsibility. Our holding, therefore, is consistent with controlling common law, and does no violence to the separation of powers doctrine or the prerogatives of the Legislature.
¶ 43. Finally, the dissent claims that the “moral blameworthiness” rationale for barring an insanity defense based upon the recent, voluntary use of illegal drugs is “suspect” here because the taking of drugs may not have been “entirely voluntary.” Post, ¶¶ 66-67. In fact, however, defendant did not claim below, and does not argue here, that his consumption of illegal psychoactive drugs was involuntary. Rather, defendant has consistently maintained that the insanity defense should be available notwithstanding his voluntary use of illegal drugs if the drugs resulted in a settled insanity or interacted with a preexisting mental condition to cause insanity. Defendant’s implicit concession is consistent with Dr. Linder’s report, based on interviews with defendant and others, which indicates that defendant had been consciously experimenting with the mind-altering effects of illegal drugs out of “intellectual curiosity.” Accordingly, the dissent’s argument is simply irrelevant to this case. Furthermore, although the dissent cites articles suggesting a causal connection between mental illness and compulsive drug or alcohol use, most courts have rejected the proposition that mental illness that predisposes a defendant to drug or alcohol abuse may justify a finding of involuntary intoxication. See, e.g., Evans, 645 P.2d at 159-60 (rejecting claim that an internal compulsion to drink may support involuntary intoxication or insanity defense); See v. State, 757 S.W.2d 947, 950 (Ark. 1988) (noting that “most jurisdictions have held that an irresistible compulsion to consume intoxicants caused by a physiological or psychological disability does not render the ensuing intoxication involuntary”); State v. Palacio, 559 P.2d 804, 806 (Kan. [59]*591977) (rejecting claim that compulsion to drink rendered defendant’s intoxication involuntary); State v. Bishop, 632 S.W.2d 255, 259-60 (Mo. 1982) (rejecting argument that drugged condition of defendant was involuntarily produced where it was caused by defendant’s addiction); see generally Dressler, supra, § 24.02[A][2], at 321-22.
III.
¶ 44. The fundamental principle underlying the insanity defense is that one should not be punished for criminal acts for which one is not responsible. Consistent with this principle, it is universally recognized that a defendant who intentionally consumes drugs or alcohol resulting in a psychotic state will not be relieved of responsibility for his or her criminal acts. The question presented by this case is whether we are willing to relieve a defendant of criminal responsibility whose psychosis allegedly emerged from a mental illness triggered by the defendant’s voluntary use of illegal hallucinogenic drugs for a period of two months preceding the crime. As explained above, we conclude that the law may reduce an individual’s culpability in such circumstances, but will not excuse it. Like any other individual asserting an insanity defense, however, defendant remains free to prove that he was not responsible for his conduct as the result of an independently preexisting mental disease or defect that rendered him unable to appreciate the criminality of his acts or to conform his conduct to the requirements of law.
The trial court order denying the State’s motion to preclude evidence at trial regarding defendant’s diminished capacity due to voluntary use of illegal drugs is affirmed. The trial court order allowing defendant to present an insanity defense based on the voluntary consumption of illegal drugs that activate a latent mental disease or defect is reversed. The case is remanded for further proceedings consistent with the views expressed herein.