RESUMEN
Objective To establish a method of sperm DNA extraction in mixed stain by using DNase-Ⅰ purificationcombined with alkaline lysis method in forensic science.Methods 79 mixed stain samples of criminal cases were collected.Sperm DNA was extracted using the purification of DNase-Ⅰ binding alkaline lysis method.16 STR loci were genotyped with fluorescent multiplex amplification system.The typing results were compared with that of extracted using two-step differential extraction procedure.Results Of all 79 mixed stain samples,64 samples were genotyped successfully by using DNase-Ⅰ purification combined with alkaline lysis method while 57 samples were genotyped successfully with two-step differential extraction procedure.There was significant difference between two methods(P=0.039).The purification of DNase-Ⅰ binding alkaline lysis method had a higher success rate and lower cost than that of two-step differential extraction procedure.Conclusion Purification of DNase-Ⅰ binding alkaline lysis method can increase the typing success rate of the mixed stain samples.The method is simple,rapid and easy to be automated,and suitable for forensic identification test.