Computers, Privacy & the Constitution

GPS investigation found illegal in Japan's Supreme Court

-- By KosukeUeno - 22 Mar 2017

Japan’s Supreme Court Decision on GPS Investigation

On March 15, 2017, just a week ago, the Supreme Court of Japan held that collection of a suspect’s location data using the global positioning system (GPS) by police officers in criminal investigation without a warrant is illegal due the infringement of privacy right. It was a first decision on this issue by Japan’s highest court.

The case was about defendants who were indicted for repeated car theft. During the investigation, the police officers attached 16 GPS tracking devices to the vehicles belonging to defendants and tracked the location of the devices more than 1,200 times over a period of six months without obtaining a warrant.

The Supreme Court not only pointed out that police officers require to obtain a warrant, but it also even requested the lawmakers to swiftly react to the ruling and make new laws to regulate GPS use in investigation so that fair criminal procedures will be guaranteed to some extent. In fact, it is rarely seen in Japan’s court decisions to push such legislation.

There have been no provisions in criminal procedural laws in Japan particularly concerning GPS tracking devices used in investigation, and the National Police Agency issued an internal notice to local police departments in 2006 that deemed GPS investigation as “voluntary investigation” which do not require a warrant under Japan’s criminal procedural laws. However, the court rejected this investigator’s interpretation and found GPS investigation as “compulsory investigation” which require a warrant. On the same day of the Supreme Court decision, the National Police Agency issued an internal notice to the police across the country to refrain from GPS investigation.

Why GPS Investigation Is a Problem?

The primary rationale from investigator’s perspective to justify the usage of GPS devices in investigation is that the degree of privacy infringement is not very high considering the fact that GPS devices attached to vehicles only detects the movement of the devices on public streets.

This is a similar analogy with the grounds that the right to refuse to be photographed is not violated when people are exposing their faces in front of other people in public places. However, can we say that there is no or low expectations of privacy because we are seen on public streets by others just for a short period of time?

I personally believe that the usage of GPS device in investigation would have the risk to endanger the privacy much more easily for the following three reasons.

First, the degree of the infringement of privacy is significantly high compared to other traditional investigating method. As long as the police can replace the battery, the GPS tracking device will be available 24 hours a day, 365 days a year to monitor a person’s behavior, which can never be done by individual police officers.

Second, the information captured by GPS investigation could be very sensitive and private. An investigating authority can monitor our location whether we are in private or public places. By collecting the location data, it would enable for police to record all of individual’s data relating to their hobbies, relationship with others, ideological beliefs and other very sensitive information.

Third, the use of data obtained by GPS tracking devices is often kept in secret. If the investigation authority can use individual’s location data obtained by GPS devices for any purpose and for any period of time only on their discretion, it could mean that legal regulations would not be surpassed. That is because whether it will be used as evidence in criminal trials like this case is uncertain. In fact, a person who is not prosecuted yet have incidentally found a GPS transmitter and filed a civil action against the police.

Scope of the Court Decision

The Supreme Court ruled the illegality of the use of GPS devices focusing on the degree of infringement of privacy. However, what was found illegal in this ruling was with respect to acquisition of location information by GPS device by physically attached to the car of the suspects, not with respect to acquisition of location information by intervening in the communication means of mobile phone.

Therefore, although there has been no Supreme Court’s decision yet on the legality of the acquisition of the location information of an individual’s smartphone, it is expected that such investigation will still be legal and possible without obtaining a warrant in the future for the police.

In fact, major smart phone companies in japan, in reaction to the ruling, already expressed the opinion that there currently responding in accordance with laws and regulations and will respond in the future as well.

Situations in the United States

This situation is somewhat similar in the United States. The U.S. Supreme Court held in United States v. Jones (2012) that the installation of GPS devices on Jones’ vehicle without a warrant constituted an unreasonable search under the Fourth Amendment. The Court rejected the government’s argument that there is no reasonable expectation of privacy in a person’s movement on public area.

On the other hand, the U.S. Court of Appeals for the Sixth Circuit found in United States vs. Skinner (2012) that tracking GPS signals emitted from a suspect’s mobile phone and monitor the location information without a warrant does not violate the Fourth Amendment.


Science and technology are progressing day by day. When a new effective investigation method is invented, first of all, it is necessary to create appropriate rules to keep balance with fundamental rights especially the Fourth Amendment. Investigation method using GPS device is indeed very effective. That is why the degree of privacy infringement is extremely high at the same time.

Therefore, instead of banning it, it is essential to have a mechanism that “reduces” the risk of such infringement by adopting ex-ante regulations. To that extent, the Supreme Court decision can be evaluated as requesting ex-ante regulations by the court for GPS investigation and avoiding arbitrary operation by investigative authority.

Or, it could be said to be a decision to accept the US Supreme Court's position in Jones, which really makes no sense in a world of smartphones, as you say, and freezes it in time, in effect making the police surrender one technique that will not be very important in future, on principles which do not interfere with what now really matters.

The surprising degree of activism by the Japanese Supreme Court, then, could be read instead as a more usual attempt to represent a consensus already decided upon, conservative and depending on misdirection of the eye, which is never the way Japanese political processes work.

In this case, we can say that the process of intellectual fertilization is more understandable, and we just wish Supreme Court justices would stop going to the same conferences together, and picking up bad habits about how to resist the realities of change.

In truth, of course, a more balanced perspective is probably correct. I don't think you need to revise the essay in order to account for these possibilities, given what you already have said, or at least hinted. But, being American, I favor less indirect ways, and would prefer you made a draft that said what I think we both probably suspect, which is that this isn't quite as activist move by the Supreme Court as it looks.

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r3 - 04 May 2017 - 22:09:05 - KosukeUeno
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