Investigators are scrambling to retrieve erased data from more than a dozen smartphones confiscated from the suspected ringleaders of a series of burglaries across Japan. But digital forensics experts say recovering such data, which would be key in building the case, could be an extremely tall order.

Tokyo’s Metropolitan Police Department is working to recover potential lost data after Philippine immigration authorities handed over about 15 smartphones to Japanese authorities, as well as tablets the suspects in Manila had been using — allegedly to give instructions to rank-and-file collaborators in Japan.

Some of the devices, however, were found to have almost no stored data and are believed to have undergone a factory reset, which would require complex digital forensics to recover.

“The hurdle to restore such data is quite high,” said Shigetsugu Yamada, a director at U&I Advisory, a Tokyo-based firm specializing in digital forensics. "This is a question of fragmented pieces of information (from the device) being partially recovered, so it would be extremely difficult."

Yamada noted that the level of difficulty would vary depending on the type of phone used, adding that it would be almost impossible to recover data from an iPhone and that retrieving data from an Android device would also be a highly complicated process.

The four suspects, all deported from Manila last week, had allegedly been careful not to leave digital traces of their operation, communicating through Telegram, an encrypted messaging app which allows messages to be automatically deleted after a certain period of time.

Tetsutaro Uehara, a professor at Ritsumeikan University’s College of Information Science and an expert on digital forensics, said deleted files on smartphones are generally more difficult to retrieve than files on computers.

Unless users have their files backed up to a cloud network, which many actually do, chances of regaining access would be slim, Uehara said.

“We won’t be able to know if data is backed up in the cloud just from looking into a smartphone device itself, so (the police) would have to find out from the suspects,” Uehara explained.

He also speculated that the suspects are aware that there is some data remaining in their smartphones.

“Even if they try to erase data, cell phone systems, including backups, are now intricate with links to the cloud. Where the data is kept would depend on how careful the suspects are,” Uehara added.

In the recent wave of crimes, often referred to as the “Luffy” case due to the name used by the ringleader or ringleaders, the men are suspected of orchestrating a series of robberies from an immigration detention center in Manila.

The actual robberies are thought to have been conducted by Japanese nationals who were recruited via social media to be foot soldiers in high-pay part-time gigs targeting elderly people across the country.

Information from Kyodo added