Male DNA typing from 25-year-old vaginal swabs using Y chromosomal STR polymorphisms in a retrial request case.

We report here the application of Y chromosomal DNA analysis in a retrial request case, raised officially by Sapporo High Court, Japan, of a condemned criminal whose capital punishment has been suspended. DNA was extracted from mixed seminal/vaginal secretion stains collected 25 years ago from two raped and murdered victims, and Y chromosome STR loci (DYS19, 390, 393, YCAII) were amplified and sequenced to clarify the DNA type of the rapist. Alkaline proteinase and sodium hydroxide were used before phenol/chloroform extraction to achieve high quality DNA from very old samples. In addition, amplified fragments of DYS19, DYS390, and DYS393 were sequenced using an automated DNA sequencer. Four Y STR DNA types detected from vaginal swabs were found identical to those of the accused criminal and confirmed that the two rape and murder cases had been committed by the same person. Sapporo High Court accepted the results and rejected the retrial request in February 1998.