An appeal court implied a strong warning about the trustworthiness of DNA analyses that are carried out during criminal investigations when it overturned a lower court's conviction of a man for raping a woman in Kagoshima in 2012 and acquitted him.
The Miyazaki branch of the Fukuoka High Court handed down the ruling after DNA analysis conducted during an appeal trial on traces of semen left in the woman's body proved that they were those of a person other than the defendant.
The ruling even pointed to the possibility that police concealed the results of its DNA analysis and criticized prosecutors for performing their own DNA tests without notifying the court.
DNA examination results can be conclusive evidence. If law enforcement authorities were to arbitrarily treat such analyses, it would be impossible to ensure fairness in criminal procedures. Police and the district public prosecutors' office that investigated the case should scrutinize the processes of their respective analyses.
The prefectural police initially concluded that it was impossible to identify the DNA type because the amount of semen was too small. However, the DNA type in the sample was identified in analyses that were conducted during the appeal trial at the request of the defense counsel. It turned out that the prefectural police dumped all the DNA solution leftover after the force conducted its analyses and also discarded notes recording the results of the analyses.
Noting that the prefectural police's handling of DNA tests was highly questionable, the appeal court even pointed to the possibility that the police force reported that it was impossible to identify the DNA type in the sample after finding that the DNA type detected in the sample did not match that of the accused.
After the outcome of DNA analysis in favor of the defendant was announced, the prosecutors' office conducted another analysis and spent the precious leftover sample. The ruling also raised suspicions that prosecutors may have even intended to cover up the fact that they conducted their own DNA analysis if its outcome was disadvantageous to them.
The ruling suggests that the court has a sense of distrust in law enforcers who tend to arbitrarily deal with DNA analyses.
The precision of DNA analyses has dramatically improved in recent years and the same type of DNA can be found in only one in every 4.7 trillion people. It is fresh in people's memory that the latest DNA analysis technology was instrumental in opening retrials of a man imprisoned in the Ashikaga murder case and another serving a life prison term over the killing of a female employee of Tokyo Electric Power Co. and acquitting them. The DNA records of more than 300,000 individuals have been registered in the National Police Agency's database.
What is worrisome is that the management of DNA samples, such as collection and storage, is left entirely to the discretion of police. In the Ashikaga case, law enforcers came under fire for using up DNA samples and storing other samples in a sloppy way. The outcome of DNA tests can serve as conclusive proof, but also lead to irreparable consequences.
Several members of a special subcommittee in the Justice Ministry's Legislative Council, which worked out a plan to reform the criminal justice system in 2014, pointed to the need to enact legislation that provides for specific methods of collecting and storing DNA samples, but the panel failed to hold in-depth debate on the issue.
It is essential to involve third parties in DNA tests to make sure such examinations are conducted in an appropriate manner. The time is ripe for the government to invite experts to consider legal regulations on DNA analyses in criminal investigations.