Evaluation of forensic examination of extremely aged seminal stains

• The current forensic examinations could be applied to extremely aged seminal stains.
• All samples were positive in the prostatic acid phosphatase and semenogelin tests.
• Sperm heads were identified in all samples.
• PRM2 mRNA was detected in three of five samples.
• Five STR loci were detected in the 56-years-old sample.

The results of forensic tests, such as semen identification and short tandem repeat (STR) analysis of extremely aged seminal stains from unsolved sex crimes can provide important evidence. In this study we evaluated whether current forensic methods could be applied to seminal stains that were stored at room temperature for 33–56 years (n = 2, 33 years old; n = 1, 41 years old; n = 1, 44 years old; n = 1, 56 years old). The prostatic acid phosphatase (SM-test reagent), microscopic (Baecchi stain method) and semenogelin (RSID™ Semen Laboratory Kit) tests were performed as discriminative tests for semen. In addition, the mRNA levels of the semen-specific proteins semenogelin 1 (SEMG1) and protamine 2 (PRM2) were investigated. STRs were analyzed using the AmpFlSTR® Identifiler™ PCR Amplification Kit. All samples were positive in the prostatic acid phosphatase and semenogelin tests, and sperm heads were identified in all samples. The staining degree of the aged sperm heads was similar to that of fresh sperm. Although SEMG1 mRNA was not detected in any sample, PRM2 mRNA was detected in three samples. In the STR analysis, all loci were detected in the 33-years-old sample and five loci were detected in the 56-years-old sample. We confirmed that current forensic examinations – including STR analysis – could be applied to extremely aged seminal stains. These results could be useful for forensic practice.