Abstract: Objective To study the effect of the double-digest and magnetic beads method for DNA extraction from 3 types of decomposed tissues. Methods DNA of cartilages, nails and joint capsule in 91 highly decomposed corpses which had not been extracted by common magnetic beads method, were prepared with the double-digest and magnetic beads methods, and quantified with Quantifiler^TM kit, followed by amplification with Sinofiler^TM kit or Minifiler^TM kit. Results DNA concentration extracted from the 91 highly decomposed cartilages, nails and joint capsule samples was 0-0.225 ng/μL. Sixty-two samples whose DNA concentration were more than 0.020 ng/μL had obtained 9 or more STR loci successfully. The detection rate was 68.13%. Conclusion The successful rate of STR genotyping for the 3 types of decomposed tissues can be significantly improved by the double-digest and magnetic beads methods.

Key words: forensic genetics, cartilage, nails, joint capsule, decomposed tissue, magnetic beads methods, twice-digest