RESUMO
Human body fluids such as blood and saliva represent the most common source of biological material found at the scene of the crime. Limitations of existing presumptive tests for body fluid identification in forensics, which are usually based on chemo luminescence or protein analysis, are expected to be overcome by DNA-based methods. Our study aiming mainly for sex determination of blood samples found at the scene. of the crime at different temperatures up to 40°C and after different times up to 3 months if they were discovered on cotton fabrics or wooden pieces. For this work 20 blood samples from different females and males were collected in test tubes without any anticoagulant substance, then samples of each sex were further subdivided into 4 main groups: gp 1 for immediate DNA extraction, PCR and identification of amelogenin, SRY, and androgen receptor sequences, gp 2 samples left at room temperature for 4 days, gp 3 samples put on cotton fabrics pieces and preserved at 21°C and 40°C for successive 7 days and 3 months. Gp 4 samples put on pieces of wood and preserved at 21 °C and 40°C for successive 7 days and 3 months. Then all samples were subjected to DNA extraction, PCR and identification of amelogenin, SRY, and androgen receptor sequences. Results showed that coagulated blood samples and blood stains from cotton fabrics are suitable for DNA extraction and identification up to 40°C and up to 3 months while samples found at wood surfaces cannot resist high temperatures up to 40°C either for short or long time