TOKYO (TR) – The National Police Agency (NPA) announced Thursday the results of a special probe into the Saga Prefectural Police, revealing that a former crime lab technician improperly handled or fabricated evidence in nearly 240 DNA tests over a span of several years.
According to TBS News (June 4), Takehiro Tominaga, 43, a former employee at the Saga Prefectural Police Crime Laboratory, was previously indicted without arrest on charges of forging and utilizing false official documents after it came to light that he had systematically doctored DNA test results.
According to the NPA’s special inspection, which began last October to address what it called a “serious issue shaking public trust in the police,” Tominaga was solely responsible for 643 DNA tests. Of those, investigators confirmed “inappropriate handling” in 239 cases.
The misconduct, which began in August 2016, involved 20 different types of violations. In seven categories, the technician’s actions directly threatened the integrity of the investigations. These included pretending to test samples he hadn’t actually used, and losing leftover evidence only to substitute it with fake materials to cover his tracks.
Of the 239 compromised tests, 192 were conducted for criminal investigations, while 47 were for non-criminal matters such as identifying corpses or missing persons.
No false arrests
The NPA stated that the fabricated results did not lead to any false arrests, wrongful detentions or innocent people being handed over to prosecutors.
However, authorities admitted it remains “unknown” if the botched tests allowed actual perpetrators to slip through the cracks in 37 cases — some of which have already passed the statute of limitations. In 29 of those cases, no original evidence remains to conduct a re-test. In eight others, the NPA noted that a proper DNA match might have been found had Tominaga performed his duties correctly.
The NPA’s findings severely undermine an earlier internal probe by the Saga Prefectural Police, which had only identified 130 problematic cases. Backed by a 35-person team including university professors and national lab experts, the NPA uncovered 110 additional violations. The agency noted that the local police lacked the expertise to conduct a proper audit and had inaccurately grouped multiple violations within single cases.
Investigators concluded that Tominaga lacked basic ethics as a forensic investigator, actively manipulating evidence to hide his own errors. However, the probe also highlighted systemic failures within the department, citing a complete lack of oversight during the testing process and heavy workloads—such as forcing the lab to run DNA tests on cases where the suspect was already known through other evidence.
To prevent a recurrence, the NPA plans to appoint external “DNA testing advisors,” establish a multi-person verification system, triage the necessity of incoming test requests, and review how crime labs are structured nationwide.
