Abstract: Objective To extract sperm DNA from mixed stain by the modified differential lysis method combined with silicon bead method and to evaluate its application value. Methods Fifty-two mixed stains containing female STR genotypes detected by differential lysis method were collected. The sperm DNA was extracted by the modified method combined with silicon bead method, then genotyped with the IdentifilerTM Kit, and compared with the results of genotyping by the conventional differential lysis method as control. Results Of the 52 samples, 38 samples with sole male STR genotypes in all loci were detected. The detection rate of male STR genotypes was 98.08% through the modified method combined with silicon bead method. Conclusion The modified differential lysis method combined with silicon bead method can be used in extraction of sperm DNA from mixed stain.

Key words: forensic genetics, mixed stain, two-step method, silicon method