DREBEN, J.

After taking chlordiazepoxide, a medication prescribed by his physician, the defendant was involved in an automobile accident. At his trial on complaints charging him with operating a motor vehicle "while under the influence of" drugs (G.L.c. 90, § 24[ a]) and with operating "a [motor] vehicle negligently so that the lives or safety of the public might be endangered" (G.L.c. 90, § 24[ a]), the defendant was precluded, on objection by the Commonwealth, from introducing evidence that he had no knowledge of the effects of the medication and that he had not received warnings about using the drug before driving. The defendant was also unsuccessful in obtaining an instruction that the Commonwealth was required to prove that he knew or should have known that the drug might affect his ability to drive safely. The defendant was convicted of both charges. The trial judge imposed fines but stayed their payment pending appeal. We conclude that the excluded evidence was relevant and reverse the convictions.

The applicable portion of G.L.c. 90, § 24(1) ( a), is set forth in the margin. The Commonwealth contends that the provision is to be read as a "public welfare" statute imposing strict liability notwithstanding "innocent intent." See Commonwealth v. Buckley, 354 Mass. 508, 510 (1968). On this reading, it is irrelevant whether an accused knows or has reason to know that a drug prescribed by his physician may affect his driving ability. The act itself, i.e., driving under the influence of drugs, irrespective of fault, is the crime, and is punishable by imprisonment for up to two years.

We note at the outset that, at least in some cases, the literal wording of the statute is not to apply. For example, it cannot seriously be contended that the Legislature made it a crime to be forced at gunpoint to take drugs and drive or to drive after having unknowingly been slipped a drug within the statutory definition. At best, the statute is expressed elliptically.

The main thrust of G.L.c. 90, § 24(1) ( a), is directed at the voluntary consumption of alcohol or drugs whose consequences are known or should be known to the user. This construction is borne out by Commonwealth v. Dale, 264 Mass. 535, 537 (1928). Writing at a time when § 24 referred only to intoxicating liquor, the court stated, "The Commonwealth had the burden of proving not only that the defendant was drunk, but also that this condition was caused by the voluntary use of intoxicating liquor" (emphasis supplied). The Dale language is persuasive because "[a] person should not be criminally liable for operating a motor vehicle while under the influence of liquor or drugs if his consumption of such liquor or drugs was not voluntary. The punishment for this crime is too severe to render it a general welfare offense with consequent `strict liability'. . . ." Nolan, Criminal Law § 555, at 363 (1976) (discussing Dale).

Although the circumstances of a person who drives after taking a prescription drug unaware of its possible effects differ significantly from those of a person forced to drive after having a potion rammed down his throat or after being tricked, such circumstances also differ substantially from those of a person who drives after voluntarily consuming alcohol or drugs whose effects are or should be known. The law recognizes the differences, and authorities have characterized as "involuntary intoxication by medicine" the condition of a defendant who has taken prescribed drugs with severe unanticipated effects. See LaFave Scott, Criminal Law § 45, at 348 (1972); Perkins, Criminal Law 897 (2d ed. 1969) ("such intoxication is involuntary, because the patient is entitled to assume that an intoxicating dose would not be prescribed"). See also Commonwealth v. Sheehan, 376 Mass. 765, 771 n. 6 (1978), where the court noted that no evidence had been offered that the consumption in that case was involuntary, and pointed out that "[d]ifferent considerations may well be appropriate in determining criminal responsibility where a defendant's conduct is affected by a forced, an unknowing, or a lawful consumption of drugs."

Although there are few cases involving unanticipated effects of prescription drugs on a defendant's driving ability, and although each case depends on the specific statutory provision involved, the concept of "involuntary intoxication" has been applied to motor vehicle violations of the type under consideration in the present case. Authorities elsewhere indicate that such a nonvoluntary taking of a drug excuses certain motor vehicle offenses. See, e.g., People v. Koch, 250 A.D. 623, 624, 625 (N.Y. 1937); Burnett v. Commonwealth, 284 S.W.2d 654, 658 (Ky. 1955); Kaiser v. Suburban Transp. Sys., 65 Wn.2d 461, 466-468 (1965). See also State v. Altimus, 306 Minn. 462, 469-470 (1976). Cf. State v. West, 416 A.2d 5, 8-9 (Me. 1980). Contra Jackson v. State, 397 P.2d 920, 923-924 (Okla. Crim. App. 1964); State v. Hill, 31 N.C. App. 733 (1976) (strict liability but cough syrup ingested was not a prescription drug).

The question remains, however, whether the Massachusetts Legislature in § 24(1) ( a) intended to penalize driving after such consumption, even if characterized as nonvoluntary. In Commonwealth v. Kraatz, 2 Mass. App. Ct. 196, 200 (1974), we noted that the history of § 24 is "a patchwork of judicial decisions and legislative engraftments which beclouds any clear perception of legislative intent." Nevertheless, there is some indication, both in legislative material and in judicial decisions, that § 24 is not intended to impose criminal liability on unknowing defendants.

Of particular significance is the Third Report of the Judicial Council of Massachusetts, 1927 Pub. Doc. No. 144, at 35-37 (Report). That Report was subsequent to the decision in Commonwealth v. Pentz, 247 Mass. 500 (1924), one of the cases relied upon by the Commonwealth here. At the time of Pentz, the provision dealing with driving to endanger (now G.L.c. 90, § 24 [ a]) did not contain the word "negligently." The Pentz court held that "[i]t is [the] act which is penalized. The intent with which the act is done is an immaterial factor. It is irrelevant whether the act is negligent, or not." 247 Mass. at 509. At the request of the Massachusetts Senate, the Judicial Council investigated a bill designed to negate the construction adopted by the Pentz court. Describing the bill as "intended to avoid the liability of perfectly innocent and well-intentioned careful persons to criminal proceedings," the Council pointed out that the construction given to the statute in Pentz and other cases may make a person "criminally liable to imprisonment under circumstances which . . . would not subject him to a liability for damages in a civil proceeding." Report, supra at 35, 36. The Council recommended passage of the bill, stating, "We do not think the [L]egislature could have intended to subject a man to criminal liability for imprisonment if by accident a situation arises without fault on his part. . . . The tendency to create criminal liability in cases in which there is no criminal element or intent, express or implied, seems to us mistaken." Id. at 37. In 1928, St. 1928, c. 281, § 1, was enacted, adopting the Council's recommendation.

While the Council was addressing the provision now found in § 24(2)( a), its arguments apply with equal vigor to § 24(1)( a). We also think it significant that, as set forth in the margin, the Legislature and recent judicial decisions have avoided a construction which would impose imprisonment without fault under other parts of § 24 and under other provisions of the motor vehicle laws.

Our conclusion is strengthened by a rule of construction, followed in Massachusetts, which requires particular clarity of language before finding a legislative intent to create a "public welfare" offense punishable by a severe penalty. Because traditionally, at common law, some element of intent or knowledge was required before punishment could be imposed, see Morissette v. United States, 342 U.S. 246, 250-251 (1952), and because due process considerations may, in some cases, require some degree of notice, see Lambert v. California, 355 U.S. 225, 228 (1957); Commonwealth v. Crosscup, 369 Mass. 228, 235 n. 6 (1975); Commonwealth v. Jackson, 369 Mass. 904, 916 (1976), courts are reluctant to infer a legislative intent to impose absolute liability. "[I]n the absence of specific words saying so," it is not supposed "that the legislature intended to make accidents and mistakes crimes." State v. Brown, 38 Kan. 390, 393 (1888). In Commonwealth v. Murphy, 342 Mass. 393, 397 (1961), the Supreme Judicial Court stated, "An intention to create such an offence should appear in clear and unambiguous language." Where the offense permits the imposition of a severe penalty, here as much as two years' imprisonment, "it would take unusually clear legislative language to lead us to the view that knowledge is not required for a conviction. . . ." Commonwealth v. Buckley, 354 Mass. at 511-512. See also Commonwealth v. Crosscup, 369 Mass. at 234. Cf. Morissette v. United States, 342 U.S. at 256. Compare Simon v. Solomon, 385 Mass. 91, 100-103 (1982). Contrast Commonwealth v. Minicost Car Rental, Inc., 354 Mass. 746, 748-749 (1968); Commonwealth v. Brady, 370 Mass. 630 (1976) (minor penalties).

No such clear language appears in G.L.c. 90, § 24(1)( a). Accordingly, we hold that it was error to preclude the defendant from introducing evidence that he did not know of the possible effects of the medication on his driving ability, that he did not receive warnings as to its use, and that he had no reason to anticipate the effects which the drug induced. His failure to receive warnings from his physician and pharmacist, if there is evidence of such failure, is relevant both to the charge of driving under the influence of drugs (G.L.c. 90, § 24[ a]) and to the charge of negligence (G.L.c. 90, § 24[ a]).

Since we conclude that the defendant is entitled to a new trial, we need not consider whether the form of the requested instruction as to the defendant's knowledge was adequate to preserve this issue on appeal. Compare Commonwealth v. Larmey, ante 281, 285 (1982), with Commonwealth v. Sherry, 386 Mass. 682, 697 (1982). The defendant, on a new trial, will be entitled to an instruction that he may not be convicted under G.L.c. 90, § 24(1)( a), unless he knew or had reason to know of the possible effects of the drug on his driving abilities.

We consider briefly the other instructions sought by the defendant which may be requested on a retrial. The defendant has not cited any authority or made any persuasive argument in support of his conclusion that G.L.c. 94C, § 22( a), and G.L.c. 94C, § 21, require the broad warnings contained in his proposed instructions. To the contrary, "[t]he obligation to give adequate information does not require the disclosure of all risks of a proposed therapy." Harnish v. Children's Hosp. Medical Center, 387 Mass. 152, 156 (1982). "The remotely possible risks of a proposed treatment may be almost without limit." Id. at 155. For that reason, if for no other, there was no error in the failure to give the defendant's proposed instructions 4 and 5. As to the judge's discretion on the relevance of evidence as to the negligence, if any, of the doctor or pharmacist, see Liacos, Massachusetts Evidence 408-411 (5th ed. 1981).

Judgments reversed. Verdicts set aside.