move to the right menu  move to the main contents



Jump menu


Home > Supreme Court of Japan


2017 (A) 882

2018.05.10
2017 (A) 882
Keishu Vol. 72, No. 2
Judgment on a case in which the judgment in prior instance which denied the reliability of so-called STR DNA analysis was quashed
Case under public prosecution for breaking into residence and public indecency
Judgment of the First Petty bench, quashed and decided by the Supreme Court
Osaka High Court, Judgment of April 27, 2017
The judgment in prior instance, which found the defendant not guilty by denying the reliability of the expert opinion that the semen-like material left and collected on the crime scene contained DNA which derived from a single person whose STR types match those of the defendant, based on, among other things, the results of a so-called STR DNA analysis which was performed on the material left on the scene by analyzing the STR types detected at 15 different loci, should be found to have made significant factual errors by erring in determining the reliability of the expert opinion as a result of overlooking important reasons for the expert opinion that the material left on the scene contained DNA derived from a single person, and as a result of the court of prior instance’s inferences lacking scientific grounds (see this Court’s judgment), and should inevitably be quashed under Article 411, item (iii) of the Code of Criminal Procedure.
The first half of Article 130 and Article 174 of the Penal Code; and Article 411, item (iii) of the Code of Criminal Procedure



Penal Code

(Breaking into a Residence)

Article 130 A person who, without justifiable grounds, breaks into a residence of another person or into the premises, building or vessel guarded by another person, or who refuses to leave such a place upon demand shall be punished by imprisonment with work for not more than 3 years or a fine of not more than 100,000 yen.

(Public Indecency)

Article 174 A person who commits an indecent act in public shall be punished by imprisonment with work for not more than 6 months, a fine of not more than 300,000 yen, misdemeanor imprisonment without work or a petty fine.



Code of Criminal Procedure

Article 411 Even in absence of grounds as prescribed in the items of Article 405, the final appellate court may render a judgment to reverse the judgment of the court of first or second instance, on any of the following grounds when it deems that not doing so would clearly be contrary to justice:

(iii) There is an erroneous finding of a material fact which would have affected the judgment.;
The judgment in prior instance is quashed.

The final appeal is dismissed.
The public prosecutor’s statement of reasons for final appeal, including the allegation of violations of judicial precedents, substantially consists of allegations of factual errors which do not constitute any of the reasons for final appeal listed in Article 405 of the Code of Criminal Procedure.

However, based on the Court’s ex officio investigation of the present case considering the public prosecutor’s reasons for final appeal, the judgment in prior instance should inevitably be quashed under Article 411, item (iii) of the Code of Criminal Procedure, for the following reasons.

I. A summary of the charged facts and of the judgment in first instance and that in prior instance

1. A summary of the charged facts is as follows: At around 9:41 p.m. on February 22, 2015, the defendant, without good reason, broke into a condominium building in Sakai City, which was guarded by another person (hereinafter referred to as the “Condominium Building”), through the self-locking entrance door on the first floor by following a resident. Around the same time, the defendant exposed his penis and practiced masturbation in the corridor on the first floor in a situation where his act could have easily been perceived by many and unspecified persons, followed by exposing his penis, practicing masturbation, and ejaculating in the corridor on the second floor in the same situation, thereby committing an act of public indecency.

2. The defendant challenged his identity with the criminal. However, based on the expert DNA analysis performed by Professor and Doctor SUZUKI Koichi of the Faculty of Medicine at the Osaka Medical College (hereinafter referred to as “Suzuki’s Expert Examination”) on the semen-like material left and collected on the scene of the case (hereinafter referred to as the “Material”), the court of first instance found, as described below, that the defendant was the criminal and that the facts of the crimes stated in the charged facts existed, sentencing the defendant to one year in prison.

The Court finds that the Material is semen left on the scene by the criminal after the crime and that the DNA typing of the Material indicates that it derives from the defendant, meaning that the Material is semen of the defendant. The Court sees no reason for the defendant’s semen to be left on the scene, other than that he was the criminal who ejaculated.

3. The defendant appealed against the judgment in first instance, on the grounds of factual errors. The court of prior instance quashed the judgment in first instance and acquitted the defendant on the grounds of factual errors, holding that the suspicion of the Material having been contaminated could not be excluded, which made the reliability of Suzuki’s Expert Examination questionable and raised a reasonable suspicion as to the defendant’s identity with the criminal.

II. The Court’s decision

However, the court of prior instance’s decision described above cannot be approved, for the following reasons:

1. According to the findings and records of the judgment in first instance and that in prior instance, the facts related to the case are as described below:

(1) The criminal broke into the Condominium Building through the self-locking entrance door by following a resident who was going home. The criminal followed the resident up to the entrance of the resident’s unit by taking the stairs from the corridor on the first floor to that on the second floor while exposing his penis and practicing masturbation. Becoming aware of the criminal who was practicing masturbation, the resident shut the entrance door and called the police at 110. The police officers who soon arrived at the scene conducted an inspection of the scene, found a semen-like liquid pool on the corridor under the entrance door of the aforementioned resident’s unit, and collected the Material using special cotton swabs.

(2) In the analysis conducted at the Forensic Science Laboratory, Criminal Investigation Department, Osaka Prefectural Police Headquarters in the course of investigation (hereinafter referred to as the “FSL’s Examination”), one portion of the cotton swab to which the Material adhered was cut out and was subjected to a semen test, which revealed a large number of spermatozoa and no other specific types of cells than spermatozoa. Other tests, including an STR typing test, found that the STR and amelogenin types detected at 15 different loci matched those of the defendant’s cells collected from his mouth.

(3) Suzuki’s Expert Examination included, among others, an STR typing test performed on three DNA sample solutions extracted by cutting out two portions of the cotton swab to which the Material adhered and using a different kit from that used in the FSL’s Examination. While the STR and amelogenin types detected at 14 loci matched those detected at the respective loci in the FSL’s Examination, at the one remaining locus a third STR type was detected in addition to the two STR types matching those detected at the same locus in the FSL’s Examination. Based on these results, Suzuki’s expert opinion concluded as follows: Considering, among other things, the STR types detected at the 15 different loci, the Material contains DNA derived from a single person whose DNA types match those of the defendant. The third STR type which was detected at the aforementioned locus is considered to have derived from mutations of male germ cells and does not indicate contamination by DNA derived from (an)other person(s).

2. The judgment of prior instance held that the Material was suspected of having been contaminated by DNA derived from (an)other person(s) because, although three or more STR types are not generally detected at each locus if the material contains DNA derived from a single person, three STR types were detected at the aforementioned one locus in Suzuki’s Expert Examination, and because the Material was collected on the corridor in the condominium building, where it was possible that the Material might have been contaminated by DNA derived from (an)other person(s). In denying the suspicion that the Material had been contaminated by DNA derived from (an)other person(s), Suzuki’s expert opinion failed to provide explanations sufficient for the expert opinion to be used as a basis for fact-finding in a criminal trial.

However, based on the results of the analysis of three DNA sample solutions extracted from the Material, Suzuki’s expert opinion explains that one or two peaks representing an STR type(s) were clearly identified at each of the 15 different loci, and that the heights of the peaks correspond to the amount of DNA derived from a single person. The Court finds that this explanation, as well as the explanation about the detection of a third STR type at one locus described above, is a reasonable one supported by expert knowledge.

In contrast, the judgment in prior instance held that assuming the Material had been contaminated, it was possible that STR types that were different from those of the criminal might be detected at many loci in ways that appeared to represent the amount of DNA derived from a single person, depending on the types and amounts of STRs contaminating the Material. While expert witness Professor Suzuki denied this possibility in the examination of witnesses at the court of prior instance, the court of prior instance did not present expert knowledge which would have provided grounds for its judgment. In addition, while the judgment in prior instance pointed out that the extent of presumption provided by Suzuki’s Expert Examination was limited by the fact that a perfect match with the defendant’s STR type(s) was seen only at 14 loci, the judgment failed to specifically discuss the portion of Suzuki’s expert opinion which explains that the Material contains DNA derived from a single person based on the results of the analysis of the peaks representing STR types and the heights of these peaks detected at the aforementioned 15 loci.

Furthermore, regarding the FSL’s Examination, the judgment in prior instance held that the possibility cannot be excluded that part of the contaminated material may have been amplified in a manner that would amplify STRs of types other than the original STR types. The court of prior instance also doubted the reliability of the assumption that the Material was semen, because of the inconsistency between the results of Suzuki’s Expert Examination and those of the FSL’s Examination. However, it is unlikely that the Material had been contaminated by DNA derived from a third party(ies) other than that derived from the criminal’s semen, considering: that there were no problems with the circumstances under which the Material was collected or with the manners in which the Material was stored and analyzed; that, as described above, the semen test conducted as part of the FSL’s Examination identified spermatozoa; and that the results of Suzuki’s Expert Examination and those of the FSL’s Examination were almost consistent with each other. Eventually, the Court should find that the judgment in prior instance erred in determining the reliability of Suzuki’s Expert Examination by overlooking important reasons for Suzuki’s expert opinion that the Material contained DNA deriving from a single person, and by making inferences lacking scientific grounds.

3. For the reasons described above, the Court should find that the judgment in prior instance erred in evaluating evidence and eventually made significant factual errors, in that the judgment denied the defendant’s identity with the criminal on the grounds of the alleged questionable reliability of Suzuki’s expert opinion that the Material contained DNA derived from a single person whose DNA types matched those of the defendant. It is obvious that these errors affected the judgment, and it would be extremely unjust if the Court did not quash the judgment in prior instance.

Therefore, the Court quashes the judgment in prior instance under Article 411, item (iii) of the Code of Criminal Procedure. Based on the discussion described above, the defendant’s appeal alleging factual errors in the judgment in first instance is eventually groundless, and the Court dismisses the appeal under the proviso to Article 413 and Article 414 and Article 396 of the same code. As for the defendant’s non-payment of the court costs incurred in the court of prior instance, the Court applies the proviso to paragraph (1) of Article 181 of the same code. Accordingly, the Court unanimously decides as set forth in the main text.

In the presence of Public Prosecutor, KANNO Toshiaki
Justice KOIKE Hiroshi

Justice IKEGAMI Masayuki

Justice KIZAWA Katsuyuki

Justice YAMAGUCHI Atsushi

Justice MIYAMA Takuya
(This translation is provisional and subject to revision.)