White paper on crime 2010 Part2/Chapter1/1
All cases cleared by the police, etc. are referred to public prosecutors, although certain exceptions to the rule do exist, which include cases subject to disposition of trivial offenses (refers to the disposition of certain minor cases such as theft, fraud, and embezzlement, etc. committed by adults and predetermined by public prosecutors that judicial police officials need not refer to public prosecutors, as in accordance with the proviso of Article 246 of the Code of Criminal Procedure) and Road Traffic Act violations for which non-penal fine had already been paid. The number of persons disposed by the police as trivial offenses in 2009 was 108,032 (the number of persons disposed by the police as trivial offenses for non-traffic penal code offenses being 108,015, accounting for 32.4% of the total number of persons cleared) (Source: Criminal Statistics by National Police Agency).
In addition to investigating cases referred to them by the police, etc., public prosecutors can also initiate investigations themselves with cases that they have become aware of or about which they have received complaints/accusations and make a decision on whether to prosecute the case or not after having taken into account whether it was actually a crime and the need for punishment, etc.