Abstract: Objective To explore the feasibility of biological method to identify the biological attribute of samples at crime scene. Methods Thirty samples of ten blood stains, ten saliva stains and ten semen stains were selected, and all the samples were processed by the routine method and biomolecular method, respectively. Both RNA and DNA were isolated using DNA-RNA co-extraction technology and the mRNA was converted into cDNA using reverse transcription PCR （RT-PCR）. Three pairs of specific primers were designed for blood stain, saliva stain and semen stain based on the different target genes in three specific tissues and the primers were amplified using real-time fluorescent quantitative PCR. The differences in these biological samples were evaluated by melting temperature （Tm） values and the size of the amplification fragment. Results The Tm values of blood stain, saliva stain and semen stain were （84.5±0.2） ℃, （76.9±0.3） ℃ and （88.5±0.2） ℃, respectively. The length of PCR fragments of them was 177 bp, 134 bp and 294 bp, respectively. Conclusion Compared with the routine method, RT-PCR with real-time fluorescent quantitative PCR is highly specific, sensitive and reliable to identify the biological attribute of evidence, and can be potentially applied to determine evidence attribute in forensic practice.

Key words: forensic genetics, reverse transcriptase polymerase chain reaction, real-time fluorescent quantitative polymerase chain reaction, blood, saliva, semen