Forensic DNA profiling: state of the art

Abstract

DNA profiling is now a routine test, yet it has only been 26 years since its first use. During these intervening years, the science of DNA profiling has undergone many changes, and it will continue to do so in the future. DNA profiling in the laboratory starts with DNA extractions and is followed by quantification of the DNA, amplification of up to 23 human specific short tandem repeat loci, and separation on capillary columns. The final stage is interpretation of the data leading to reporting the DNA evidence to a court. Each of these steps has seen improvements leading to higher sensitivity from minute trace samples. Genetic markers on the X and Y chromosomes are now used for both criminal and civil investigations, along with mitochondrial DNA. Mitochondrial DNA has been used in forensic science since the 1990s because of its high copy number and particular maternal inheritance. These sex chromosome markers and mitochondrial DNA were used effectively to determine the identity or ancestry of individuals, and now other genetic markers can be used to determine certain phenotypic traits to a high degree of accuracy. Genetic testing adapted from medical and pharmaceutical sciences, such as next-generation DNA sequencing, will soon be applied to mainstream forensic science, opening new avenues in criminal investigations. This review aims to cover these key events and advancements in the field from both a historical view and current practice. Opening comments DNA profiling has revolutionized the process of forensic human identification. It is of note that this is a relatively recent addition to the forensic science tool kit and that it is constantly undergoing developments. The aim of this review is to take the reader through the processes of DNA typing, starting with DNA isolation from biological material through novel approaches and phenotypic testing. The review is written for those in forensic medicine; therefore, certain knowledge is assumed, but equally, aspects that are specific to forensic science will be emphasized and placed into the right context. For those who wish more information than can be provided within the scope of this review, there are books ranging from introductory texts 1 to those that are more comprehensive. 2,3