Forensic Science and Microbiome
Contributed by Ning Chin
Forensic science is the use of science to settle a legal argument. In criminal cases, a forensic technique is used to definitively identify the victim and the perpetrator. Deoxyribonucleic acid (DNA) that is present in most human cells and biological fluid has individualizing characteristics that allow forensic scientists to identify the person that left the DNA. DNA fingerprinting is currently widely accepted in court and is considered the gold standard in forensic science because it is highly polymorphic and thus has a high degree of individualization. The court also accepts animal DNA evidence. Unknown animal blood and tissue samples are tested to screen for endangered wildlife to track down poachers. DNA of pets can also serve as evidence of association between the suspect, the victim, the evidence, and the crime scene.
One of the most important aspects of forensic science is context. While human DNA is great at providing information regarding the identity of a person, other evidence are often needed to prove that the suspect has ill intent. Bacterial DNA might prove to be useful in these situations. Bacterial DNA has gained significant attention because next-generation sequencing has made sequencing bacterial DNA more accessible. Traditionally, scientists used culture-based methods to grow and observe bacteria on different media, but that lacks the predictive value of single organism analysis. In contrast, sequencing bacterial DNA yields genomic information to provide community structure and specific genomic information about the entire bacterial population of a specific location. In environmental samples this molecular bacterial fingerprint is definitive for specific location. This is also true of specific metabolically linked human parameters, such as obesity. Several researchers have demonstrated that every individual has a unique skin microbiome that can be used as an identification method to connect an item to its user. Researchers also showed that bacteria can be used to determine the cause of death and time of death. Bacteria can also be used to predict the source of body fluids, which is especially important in sexual assault cases. Collectively these studies suggest that measuring each bacterial species in a bacterial community can be very helpful in forensic science.