When Sound Becomes a Weapon: Japan's Supreme Court on Injury by Noise Harassment

Case Title: Case of Causing Injury

Court: Supreme Court of Japan, Second Petty Bench

Decision Date: March 29, 2005

Introduction

In an increasingly dense and interconnected world, the nature of harm one person can inflict upon another has evolved. While the classic image of a criminal assault involves physical violence, modern forms of harassment often employ intangible but deeply damaging methods. This raises a critical legal question: can a person be found guilty of the serious crime of "causing injury" not with a fist or a weapon, but with sound?

In a landmark decision on March 29, 2005, the Supreme Court of Japan confronted this question head-on. The case involved a defendant who, for over a year and a half, subjected their neighbors to a relentless barrage of high-volume noise, resulting in medically diagnosed health problems. The Court’s ruling, which upheld a conviction for the crime of causing injury, provides a definitive statement on "injury without assault" in Japanese law. It affirms that the means of inflicting harm are not limited to physical force and sets a crucial precedent for how the law addresses psychological and physiological damage caused by prolonged harassment.

Facts of the Case

The case centered on a prolonged neighborhood dispute that escalated into a campaign of acoustic warfare. From approximately June 2002 to December 2003, a period spanning about 18 months, the defendant, D, intentionally directed loud noises from their home towards the adjacent residence of the victim, V.

D's method was systematic. They placed a radio and multiple alarm clocks at or near an open kitchen window, which was the closest point in their house to V's home. For nearly a year and a half, D blasted the audio from the radio and the piercing sounds of the alarm clocks at an extremely high volume. This auditory assault was not sporadic; it occurred "day after day, night after night," often starting in the morning and continuing until late at night or the early hours of the next day.

The relentless exposure to this noise took a severe toll on V's health. The victim was diagnosed with a series of debilitating conditions, including chronic headaches, a persistent sleep disorder, and tinnitus (a constant ringing in the ears). The prognosis for these conditions was listed as "of unknown duration," indicating a serious and potentially long-lasting injury.

The Nara District Court and the Osaka High Court both found D guilty of the crime of causing injury under Article 204 of the Penal Code. They reasoned that while the noise itself was not a direct physical blow, the act of generating it continuously was socially understood to carry a realistic risk of harming a person's physiological functions—a risk that materialized in V's case. D appealed these convictions to the Supreme Court of Japan.

The Supreme Court's Decision

The Supreme Court’s Second Petty Bench dismissed the defendant's appeal and affirmed the decisions of the lower courts. In its written opinion, the Court summarized the facts and unequivocally stated that D's conduct constituted the actus reus (the criminal act) for the crime of causing injury.

The Court explicitly noted that D acted while recognizing that their actions "might cause an impairment resulting from mental stress". By knowingly creating this risk and causing the resulting chronic headaches, sleep disorder, and tinnitus, D's liability for the injury was established. The Supreme Court found the lower courts' judgment to be "just" and correct in law.

This ruling is profoundly significant as it represents only the second time the Supreme Court has explicitly affirmed a conviction for "injury without assault," the first being a 1952 case involving the transmission of a venereal disease. This 2005 decision thus serves as a modern and powerful precedent.

Legal Analysis: Deconstructing "Injury Without Assault"

To understand the weight of this decision, one must delve into the distinction Japanese criminal law draws between "assault" (bōkō) and "injury" (shōgai), and why the concept of "injury without assault" is so critical.

Defining Assault vs. Injury

• Assault (暴行, Bōkō): Under Article 208 of the Penal Code, assault is traditionally defined as the "unlawful exercise of physical force against another person's body". This includes obvious acts like punching and kicking, but case law has extended it to include the energy of sound waves, light, and heat. For example, loudly beating a drum next to a person's ear has been recognized as an assault. However, the lower court in this case determined that D's actions, being more indirect than a direct physical application of force, did not rise to the level of a criminal assault.
• Injury (傷害, Shōgai): Article 204 of the Penal Code, which defines the crime of causing injury, is notably result-oriented. It simply punishes one who "injures a person's body," without specifying the method. The prevailing legal theory and controlling case law, known as the "physiological function impairment theory," defines an injury as any act that "impairs a person's physiological (life) function or causes an adverse change to their state of health". This broad definition includes not only external wounds but also internal conditions, fatigue, dizziness, and even psychological disorders like PTSD and anxiety states. The chronic headaches, sleep disorder, and tinnitus suffered by V clearly fall within this established legal definition of injury.

The Importance of the "Without Assault" Distinction

The classification of D's actions as "injury without assault" is not merely academic; it has crucial legal consequences, particularly concerning the perpetrator's required mental state (mens rea).

• Intent Requirement: For an "injury by assault," the crime is treated as a result-based aggravated offense of assault. This means the prosecutor only needs to prove the defendant had intent for the initial assault. If an injury results, even unintentionally, the defendant is liable for the crime of causing injury. However, for an "injury without assault," the legal bar is higher. The prosecution must prove that the defendant had intent specifically regarding the resulting injury. Without this intent, the act would, at most, constitute the lesser crime of negligent injury (Article 209).
• Establishing Intent in This Case: The lower courts, affirmed by the Supreme Court, found that D possessed the necessary intent in the form of dolus eventualis, or constructive intent (未必の故意, hitsuji no koi). This means D did not necessarily desire to cause the specific injuries but was aware that their actions carried a significant risk of causing such harm and consciously chose to proceed, thereby accepting the potential outcome. The court inferred this intent from D's objective conduct:
  1. The extraordinary duration of the harassment (1.5 years).
  2. D's violent reactions toward their own family members who tried to lower the volume or turn off the devices.
  3. D's refusal to stop the noise even after being warned by police officers.
  4. The fact that after police confiscated the radio and alarms, D acquired a new radio-cassette player and more clocks to continue the harassment as before.

This pattern of behavior made it clear that D was not merely being inconsiderate but was engaged in a deliberate campaign of harassment and was fully aware of, and indifferent to, the potential for it to cause serious physical and mental harm.

The Criminal Act: A "Series of Acts"

The actus reus for injury without assault is defined as "an act that is evaluated under social common sense as having a realistic danger of harming a person's physiological functions". A single instance of loud music would likely not meet this standard. The court therefore conceptualized D's conduct as a unified "series of acts" (ichiren no kōi). The criminal act was not one press of a "play" button, but the entire 1.5-year campaign of noise, viewed in its totality. Whether such a series of acts constitutes a criminal act of injury depends on a holistic assessment of factors like the volume and quality of the sound, the time of day, the duration, and the context of the relationship between the parties.

Conclusion and Significance

The 2005 Supreme Court decision is a vital piece of modern Japanese jurisprudence. It formally recognizes that intangible forces, when weaponized through prolonged and malicious application, can constitute the actus reus for the serious crime of causing injury. The ruling provides a clear analytical framework: the act must pose a realistic, socially understood danger to health, and the perpetrator must have, at a minimum, a constructive intent to cause the resulting harm.

By viewing the defendant’s 1.5-year campaign of noise as a single, continuous criminal act, the Court demonstrated a sophisticated understanding of how harassment works in practice. This decision sends a powerful message that the law will not tolerate the use of psychological stress as a tool to inflict physiological harm and that the right to quiet enjoyment and well-being is a legally protected interest. It stands as a critical precedent in an age where the methods of causing harm are ever-evolving, ensuring that the Penal Code remains a relevant and effective shield for victims.