The Supreme Court is set to soon hand down its first judgment on whether use of global positioning systems by police without a court warrant is illegal.

The court’s 15-member Grand Bench is looking into the case of a 45-year-old man who was tracked by police using GPS devices attached to his car as part of an investigation into his alleged role in a string of group robberies in Osaka, Nagasaki and other places between 2012 and 2013.

Osaka Prefectural Police attached the GPS devices to vehicles thought to have been used by the man and others to keep track of their movements.

Police consider that investigations using such a tool do not require court warrants, and have made use of GPS devices previously before formal investigations were launched.

A Supreme Court ruling would effect the ongoing use of the policing method.

Last year, the Osaka District Court refused to accept evidence gathered during investigations into the 45-year-old man, saying that using GPS devices without a warrant amounted to a serious breach of the law.

The defendant was found guilty and given a prison sentence based on other evidence.

The man’s defense appealed to the Osaka High Court, which in March this year dismissed the appeal on the grounds that no serious breach of law took place.

It is likely that the defendant’s conviction will be maintained since the Supreme Court has no plans to launch a fresh examination of the evidence.