The Supreme Court has ruled that the collection of data through the Global Positioning System in police investigation without a warrant is illegal, and the National Police Agency immediately told police forces nationwide to halt the practice. The top court called for new legislation to cover the use of GPS by the police for investigation purpose, raising doubts about the procedure of issuing warrants for the use of GPS devices in criminal probes under current provisions of the Criminal Procedure Law. The Diet should immediately establish a legal framework to set clear-cut procedures and scope for police collection of GPS data to prevent arbitrary use of the technology by investigators.

The defendant in the case concerning serial theft committed mainly in the Kansai region in 2012-2013 contested the legality of warrantless surveillance through the use of GPS devices. The Osaka District Court ruled in 2015 that the warrantless collection of GPS data in the investigation was illegal and struck the evidence thus collected. Last year, the Osaka High Court determined that the police investigation in this case did not involve serious illegality, without handing down judgment on whether the police needed to obtain a court warrant for collecting the GPS data. The Supreme Court ruled that the warrantless GPS data collection was illegal, although it upheld the 5 1/2 year jail term on the defendant meted out by the lower courts.

During the investigation, the police installed 16 GPS tracking devices on vehicles owned by the defendant and other suspects over several months. Their action followed an internal manual issued by the NPA that allowed warrantless collection of GPS data for the investigation of such crimes as kidnapping, confinement and serial thefts in view of the need for immediate action and the difficulty of tracking suspects by other means.