A recent court acquittal of a 23-year-old Kagoshima man who had been charged with rape has again showcased the questionable handling of evidence — DNA analysis this time — by both the police and prosecutors. If the court had overlooked the suspicious behavior of investigative authorities, the man might have had to serve four years in prison due to a false charge.

Both the police and prosecutors need to review their handling of the evidence in question and make public detailed reports so that the case can serve as a lesson to ensure fairness in investigations. The outcome of the case underlines the potential risks of leaving control of physical materials for DNA tests in the hands of investigation authorities. The government should devise a system in which such materials will be kept and DNA-tested in a transparent manner.

The man was indicted on a charge of raping a 17-year-old girl in an entertainment district of the city of Kagoshima in 2012. The crime laboratory of the local police said it attempted to perform a DNA test of the semen found inside the woman's vagina but was unable to carry out an analysis because the size of the sample was too small. However, the man's DNA was detected in saliva found on the woman's breast. He said that he had no memory of what he did because he was drunk.