When Can Japanese Police Detain Someone for a Urine Sample? Legality of "Stop and Detain" (留め置き - Tomeoki) for Drug Testing

In Japan, a nation known for its stringent stance on illicit drug use, the process of obtaining a urine sample is a critical component of drug enforcement. However, when an individual refuses to provide a sample voluntarily, the actions taken by police to secure one can enter a complex legal gray area. The practice of detaining an individual, often at the scene of a stop or at a police station following "voluntary accompaniment" (任意同行, nin'i dōkō), for the purpose of obtaining a urine sample—a measure referred to as tomeoki (留め置き)—has been the subject of significant judicial interpretation, balancing the necessity of investigation against fundamental personal liberties.

The Bedrock: Voluntary Investigation vs. Compulsory Measures

Japanese criminal procedure draws a fundamental distinction between "voluntary investigations" (任意捜査, nin'i sōsa) and "compulsory dispositions" (強制処分, kyōsei shobun). Voluntary investigations, as the name suggests, rely on the cooperation of individuals and generally do not require a warrant. Compulsory dispositions, on the other hand, involve coercion or infringement upon significant individual rights and interests, thus mandating specific legal authorization, most commonly a warrant issued by a judge.

Detaining a person, even for a limited period, inherently restricts their freedom of movement. The core legal challenge with tomeoki for urine collection is determining when such a detention, ostensibly part of a voluntary investigation, crosses the threshold into an unlawful restraint or a de facto arrest, thereby requiring a warrant or other specific legal basis.

The Supreme Court's Heisei 6 (1994) Landmark Decision

A pivotal moment in shaping the legal understanding of tomeoki came with the Supreme Court's decision on September 16, 1994 (Supreme Court Decision, September 16, 1994, Keishū Vol. 48, No. 6, p. 420). This case involved a suspect (X) stopped for erratic driving under snowy conditions, with police suspecting stimulant use. X was uncooperative, refusing voluntary accompaniment to the police station unless he could drive himself, which the police deemed unsafe. Police officers took X's car keys and detained him at the roadside for over six and a half hours while they eventually sought and obtained warrants, including one for compulsory urine collection (強制採尿令状, kyōsei sainyō reijō).

The Supreme Court acknowledged that taking the car keys was initially lawful, both as a measure to facilitate questioning under the Police Duties Execution Act (警察官職務執行法, Keisatsukan Shokumu Shikkōhō) and to prevent traffic danger under the Road Traffic Act (道路交通法, Dōro Kōtsūhō). However, the Court found that the subsequent prolonged detention of X at the scene for over six and a half hours, solely for the purpose of persuading him to voluntarily submit to urine collection or accompany them to the station, exceeded the permissible limits of a voluntary investigation and was therefore illegal. It was deemed an undue restriction on X's freedom of movement.

Despite this finding of illegality, the Supreme Court did not exclude the evidence obtained from the compulsory urine collection. It reasoned that the illegality was not so "grave" as to "flagrantly disregard the spirit of the warrant principle." Factors influencing this conclusion included the high necessity of preventing X from driving dangerously due to his apparent intoxication and abnormal behavior, X's own stubborn refusal of any alternative to driving himself, and the lack of evidence that police intended from the outset to unlawfully detain him for an extended period.

Crucially, the Supreme Court's judgment also noted that "police officers, by not promptly seeking a warrant and detaining X at the scene for an extended period, acted illegally." This observation hinted at a potential justification for some period of detention if steps to obtain a warrant were taken in a timely manner. This nuance became a focal point for subsequent lower court interpretations.

Development in Lower Courts: The Emergence of the "Two-Stage Theory" (Nibunron)

Building on the Supreme Court's 1994 decision, lower courts, particularly the Tokyo High Court, began to develop what is often referred to as the "two-stage theory" (nibunron, 二分論) to analyze the legality of tomeoki in the context of urine collection. This theory distinguishes between two phases of detention:

1. Stage 1: Detention for Persuasion (Purely Voluntary Investigation Phase)
   During this initial phase, the detention's primary purpose is to persuade the individual to voluntarily provide a urine sample or to voluntarily accompany officers to a police station for that purpose. The detention remains strictly within the confines of a voluntary investigation. Any restraint must be minimal, and the persuasion cannot be coercive. The duration of this stage is limited; if the individual remains uncooperative and it becomes clear that voluntary submission is unlikely, continued detention solely for persuasion becomes unlawful.
2. Stage 2: Detention Pending Warrant Execution (Transition to Compulsory Procedure Phase)
   This phase begins when investigators, having failed to secure voluntary cooperation and believing they have sufficient grounds, decide to seek a compulsory urine collection warrant. At this point, the primary purpose of any continued detention shifts from persuasion to securing the individual's presence to ensure that the warrant, once issued, can be effectively executed. Proponents of this theory argue that the necessity of preserving evidence (urine can metabolize drugs over time) and ensuring the efficacy of the warrant process justifies a continued, albeit still non-arrest, detention.

Two key Tokyo High Court decisions illustrate the development of this theory:

• Tokyo High Court Decision, July 1, 2009 (Hanrei Taimuzu No. 1314, p. 302): This case involved a suspect detained for several hours. Police initiated procedures for a compulsory urine collection warrant about 30 minutes after the suspect was brought to the station and refused to provide a sample. The court, applying the two-stage theory, found the initial 30-minute period of persuasion lawful. Regarding the subsequent detention while the warrant was being obtained (approximately 2 hours and 58 minutes until execution), the court considered it also lawful.
  It emphasized that once the decision to seek a warrant is made, the need to secure the suspect's presence is high, given that urine metabolizes substances. The court noted that the officers had informed the suspect that they were seeking a warrant. It also considered the nature of the restraint (e.g., suspect was allowed to use his phone, meet family, door was open though guarded) and concluded that the detention was the minimum necessary to ensure warrant execution and did not exceed the bounds of a voluntary investigation. The court importantly added a fugen (supplementary comment) stating that it is desirable to establish a practice of explicitly informing the suspect when the transition to seeking a warrant occurs.
• Tokyo High Court Decision, November 8, 2010 (Kōtō Saibansho Keiji Hanreishū Vol. 63, No. 3, p. 4): This decision further solidified the nibunron. Police questioned a suspect (Y) at a roadside due to suspected drug use. After about 40 minutes of Y refusing to provide a urine sample and giving suspicious explanations, an officer informed Y they would seek a compulsory urine collection warrant and left to do so. Y remained at the scene, mostly in his car, for approximately 3 hours and 20 minutes more until the warrant was executed.
  The court explicitly divided the detention into two stages. The initial 40-minute period was deemed lawful persuasion. The subsequent period, after the officer announced the intent to seek a warrant, was also held to be lawful. The court reasoned that "once the warrant application process begins, it signifies that the suspicion of a crime has intensified to a degree where investigators deem a warrant obtainable... although it remains a voluntary investigation, it qualitatively differs from the purely voluntary investigation stage." Given the high necessity of securing the suspect for warrant execution (especially for urine which can change over time), and the fact that Y was informed of the warrant application, the court found the continued detention permissible. The police did not use significant physical force, and Y was largely left in his vehicle.

Analyzing the Nibunron: Implications and Critiques

The nibunron attempts to provide a practical framework for a common investigative scenario. Its significance lies in acknowledging a shift in the justification for detention:

• Purpose Shift: The justification for detention changes from securing voluntary cooperation to ensuring the suspect is available for the execution of a (yet to be issued but anticipated) compulsory measure.
• Heightened Necessity: The need to secure the suspect's presence is arguably greater in the second stage, as failing to do so could render the entire warrant process futile if the suspect absconds or if the evidence (urine) degrades.
• Procedural Transparency: The emphasis on informing the suspect about the warrant application aims to provide a degree of transparency.

However, the nibunron is not without its theoretical and practical challenges:

• Still a "Voluntary" Measure? Despite the "qualitative difference" noted by the Tokyo High Court, any detention before a warrant is issued and executed (or an arrest is made) legally remains within the framework of "voluntary investigation." This means that, in principle, the individual is free to leave, and police cannot use physical force amounting to an arrest to prevent them from doing so. If an individual attempts to leave during Stage 2, police are still limited to persuasion or minimal physical contact that does not constitute forcible restraint.
• Risk of "Quasi-Compulsory" Detention: Critics argue that the nibunron might legitimize a form of "quasi-compulsory" detention without explicit statutory basis. The announcement that a warrant is being sought can be inherently coercive, making an individual feel they have no real choice but to remain, even if no physical force is used.
• Duration of Stage 2: While the necessity in Stage 2 is recognized, the permissible duration is not unlimited. It is generally tied to the reasonable time it takes to diligently apply for and obtain a warrant. Delays in this process could render the continued detention unlawful. Information from practitioners suggests that obtaining a compulsory urine collection warrant can take several hours (e.g., 2 hours for internal preparation and approval, 30 minutes to an hour to reach the court, 1.5 hours for judicial review, 30 minutes to return and execute). This practical timeframe implicitly sets a soft cap on Stage 2 detention.
• Objective Grounds for Warrant: The entire premise of Stage 2 rests on the investigators having legitimate, objective grounds to believe a warrant will be issued. If the grounds are weak, the detention cannot be justified.

The Unresolved Question: Need for Specific Legislation?

The judicial development of the nibunron reflects an attempt to provide guidance in an area where the Code of Criminal Procedure is largely silent. However, relying on case-by-case interpretation of what constitutes a permissible "voluntary" detention, especially when its purpose shifts to securing presence for a compulsory measure, leads to legal ambiguity.

This has led some legal scholars and practitioners to call for specific legislation to regulate such pre-warrant detention for evidentiary purposes like urine collection. The arguments for legislation include:

• Clarity and Predictability: A statute could provide clearer rules on the grounds, duration, and permissible methods of such detention, offering better guidance to both law enforcement and individuals.
• Enhanced Safeguards: Legislation could incorporate explicit safeguards, such as stricter time limits, mandatory recording of the detention period, or enhanced judicial oversight.
• Addressing Constitutional Concerns: As noted in some commentaries, any form of pre-warrant, non-arrest detention to secure a person for a compulsory measure (even for evidence like urine, not just for arrest itself) could potentially be viewed as a form of "arrest" (taiho) under Article 33 of the Constitution, which requires a warrant issued by a competent judicial officer unless an exception applies. Current law on search and seizure warrants (which a compulsory urine collection warrant resembles) does not have an "emergency execution" provision similar to emergency arrest. Therefore, detaining someone before the warrant is physically present and executable, solely on the basis that it will be issued, is legally tenuous without specific authorization.

Possible legislative solutions might involve creating a new, limited category of temporary, judicially authorized (or subsequently reviewed) detention for the specific purpose of executing a warrant for bodily samples when there's a high risk of evidence loss. However, this would require careful drafting to align with constitutional protections.

Conclusion: Balancing Act in a Legally Sensitive Area

The detention of individuals for the purpose of obtaining urine samples in Japan, or tomeoki, remains a legally sensitive practice. The Supreme Court's 1994 decision established that prolonged detention solely for persuasion under the guise of voluntary investigation is unlawful. Subsequent lower court decisions, through the "two-stage theory" (nibunron), have attempted to carve out a practical path for investigators, allowing for continued (but still non-forcible) detention once a decision to seek a compulsory urine collection warrant is made and communicated.

This framework acknowledges the shift in purpose from persuasion to securing the individual's presence for warrant execution. However, the legal basis remains rooted in "voluntary investigation," meaning the individual is, in theory, free to leave, and any restraint must fall short of an arrest. The inherent ambiguity and the potential for coercion in this situation continue to fuel debate and underscore calls for clearer legislative guidance. Ultimately, the Japanese legal system continues to navigate the delicate balance between the state's interest in effective drug enforcement and the fundamental right of individuals to freedom from arbitrary or excessive restraint.