No Discount for Drunk Driving: A 1968 Japanese Ruling on Diminished Capacity and "Action Free in its Cause"

Decision Date: February 27, 1968

The doctrine of actio libera in causa—"action free in its cause"—is a legal tool designed to solve a classic conundrum: how to hold a person responsible for a crime committed while they lacked the mental capacity to be held responsible. The doctrine ingeniously traces culpability back to the moment the person voluntarily chose to become incapacitated, typically through drinking or drug use. A landmark 1951 Supreme Court of Japan decision had already established this principle for cases where a defendant drinks themselves into a state of total insanity. But this left a crucial question unanswered.

What about the far more common scenario where a person, through their own voluntary intoxication, enters a state not of complete insanity, but of "diminished capacity" (shinshin kōjaku)? Japanese law, under Article 39 of the Penal Code, ordinarily mandates a sentence reduction for offenders with diminished capacity. Could a drunk driver, for instance, claim this mandatory "discount" on their punishment? On February 27, 1968, the Supreme Court of Japan answered this question with a firm and decisive "no," issuing a landmark ruling that extended the logic of actio libera in causa to cases of diminished capacity and ensured that drunk drivers could not use their self-induced impairment to lessen their legal accountability.

The Factual Background: A Drunken Night Out

The facts of the case were straightforward. The defendant drove his own car to a bar for a night of drinking. He was fully aware that after he finished drinking, he would be intoxicated and would be driving again. Over the course of three to four hours, he consumed approximately 20 bottles of beer.

Deeply intoxicated, he left the bar. He then mistook a car parked nearby, which belonged to another person, A, for his own and, without permission, started the vehicle and began driving. He drove for approximately 3 kilometers while in a state where he was clearly unable to operate the vehicle normally due to the effects of the alcohol. During this drive, he also picked up a passenger, B, whom he proceeded to intimidate and extort for money and valuables.

It was later established by the courts that at the time he was committing these crimes—drunk driving and extortion—the defendant was in a state of diminished capacity (shinshin kōjaku).

The Journey Through the Courts: The Question of Mitigation

The legal issue was not whether the defendant was guilty, but whether his sentence should be reduced due to his diminished mental state.

• The Trial Court: The first-instance court found the defendant guilty. Following the standard procedure laid out in Article 39, Paragraph 2 of the Penal Code, it applied a mandatory sentence reduction on the grounds that the defendant was in a state of diminished capacity when he committed the offenses.
• The High Court: The prosecution appealed this reduction. The Tokyo High Court partially agreed with the prosecution and overturned the lower court's decision with respect to the drunk driving charge. The High Court refused to apply the sentence reduction for that specific crime. Its reasoning was a classic application of the actio libera in causa principle: because the defendant "had the intent to drive drunk at a time when his mind was not abnormal, and this ultimately resulted in him driving drunk," he was not entitled to a sentence reduction, even though he was in a state of diminished capacity at the time of the actual driving.

The defendant appealed this decision to the Supreme Court, arguing that the law was clear and that a finding of diminished capacity required the court to reduce his sentence.

The Supreme Court's Landmark Decision

In a characteristically brief but powerful decision, the Supreme Court dismissed the defendant's appeal. The entirety of its core reasoning was contained in a single, decisive parenthetical sentence:

"(Additionally, in a case like this one, even if the defendant was in a state of diminished capacity due to intoxication at the time of the act of drunk driving, when the intent to drive drunk is found to have existed at the time of drinking, it is appropriate to hold that Article 39, Paragraph 2 of the Penal Code should not be applied to reduce the sentence.)"

This statement, though brief, had profound implications. It officially extended the doctrine of actio libera in causa beyond cases of total insanity to cover the more common state of diminished capacity. The Court declared that a defendant who culpably brings about their own state of diminished capacity, having already formed the intent to commit a crime, cannot then use that diminished state to claim a legal discount on their punishment.

A Deeper Dive: The Theory of Actio Libera in Causa and Diminished Capacity

This 1968 ruling was a crucial development in Japanese criminal law, closing a significant logical gap. As legal commentators pointed out, it would be deeply inconsistent for the law to hold a defendant fully responsible if they drank themselves into total insanity (as established by the 1951 precedent), but to then grant a mandatory sentence reduction to someone who drank less and only reached a state of partial impairment. The 1968 decision ensured that the law treated both scenarios with a consistent logic, focusing on the defendant's culpability at the moment of their free and sober choice.

The ruling can be understood through two primary theoretical models that seek to explain how actio libera in causa works:

1. The "Constituent Element Model" (kōsei yōken moderu): This is the dominant view in Japanese legal theory. It argues that the legally relevant criminal act is not the crime committed while intoxicated (the "result act," e.g., the driving) but the earlier, voluntary act of becoming intoxicated (the "cause act," e.g., the drinking). Responsibility is thus anchored to a moment in time when the defendant was fully capable. In this case, the act of drinking at the bar, knowing he would have to drive home, could be seen as the beginning of the criminal act of drunk driving itself.
2. The "Responsibility Model" (sekinin moderu): This alternative view holds that the "result act" (the driving) is indeed the crime, but the legal responsibility for that act is exceptionally traced back in time to the "cause act." The defendant is punished for the drunk driving, but his culpability (intent or negligence) is assessed based on his state of mind at the time of drinking. The Supreme Court's focus on the defendant's "intent to drive drunk at the time of drinking" aligns very closely with this model.

While scholars debate the finer points of these models, both lead to the same conclusion reached by the Court. The defendant made a culpable choice while sober, and the law holds him fully accountable for the foreseeable consequences of that choice.

Conclusion: No Discount for Culpable Impairment

The 1968 Supreme Court decision is a vital addendum to the foundational law of actio libera in causa in Japan. It clarified that the doctrine is not limited to the extreme and rare cases of self-induced insanity but applies with equal force to the far more common scenario of self-induced diminished capacity.

The ruling establishes a clear and common-sense principle: a defendant who forms the intent to commit a crime like drunk driving while sober, and then voluntarily consumes alcohol to the point of impairment, cannot turn around and use that self-inflicted impairment as a basis to demand a lighter sentence. The law, the Court affirmed, judges us by the free choices we make with a clear mind, not by the actions we take after we have culpably abandoned it. It ensures that when it comes to criminal responsibility, there is no discount for self-induced impairment.