Bloodstain Evidence: From Human Blood Identification to DNA Profiling - Abstract
Stains observed on a crime scene may correspond to biological fluids and therefore contain DNA which can identify a suspect or a victim as well as exonerate an innocent individual. However, fluids at a crime scene may be difficult to detect with the naked eye and may require specific identification procedures including alternative light sources. After a bloodstain has been evidenced, specific techniques (mainly chemical which, in contact with blood, change color or induce fluorescence or chemiluminescence) are used to proof the presence of human blood. Since blood evidence can help to solve the case, it is essential to adequately collect and preserve biological specimens. Continuous technological progress in biology has led to major developments in the field of forensic DNA profiling in the past 10 years. Restriction fragment length polymorphism (RFLP) profiling may be considered as the first generation of DNA analysis methods. It is no longer used as it requires large amounts of DNA, and because degraded samples cannot be analyzed with accuracy. Technological approach was then based on Polymerase Chain Reaction (PCR) techniques and PCR-RFLP. Modern DNA analysis methods now include Short Tandem Repeat (STR), Single Nucleotide Polymorphism (SNP), mitochondrial DNA (mtDNA) analyses and DNA methylation studies. In this review we analyze some of the recent progresses made in the forensic analysis of DNA. Among these, Next Generation Sequencing (NGS) now has the potential to expand the capabilities of information on STR alleles including DNA database construction, ancestry and phenotype prediction.