Forensic pathology and investigation methods

Forensic Pathology: Forensics and DNA

DNA is part of the building blocks of human life and individuality: "DNA is present in nearly every cell of our bodies, and we leave cells behind everywhere we go without even realizing it. Flakes of skin, drops of blood, hair, and saliva all contain DNA that can be used to identify us" (Norrgard, 2008). DNA has long been a major part of forensics testing used in criminal cases for over forty years. "At its inception, DNA testing could only be performed by laboratories with molecular diagnostic capabilities" (Calaluce, 2010, p.2). The controversy surrounding DNA testing that made it more heavily scrutinized when it first debuted largely revolved around the fact that it was considered a "soft science" and that DNA evidence was viewed as simply not as reliable as other types. However, this controversy has since been eliminated: and there is absolutely no valid scientific reason to doubt the accuracy of forensic DNA testing. However, it is important to acknowledge that when doing something like testing a DNA fingerprint and assessing the likelihood of a particular match between a suspect and a crime scene is indeed an intricate process that revolves around probability as well.

DNA fingerprinting is a term which has come up in the last decade or so, due to its power and the weight that it carries, but many people are still unsure of what it means and signifies. "In short, it is a technique for determining the likelihood that genetic material came from a particular individual or group. 99% of human DNA is identical between individuals, but the 1% that differs enables scientists to distinguish identity. In the case of the grapes, scientists compared the similarities between different species and were able to piece together parent subspecies that could have contributed to the present prize-winning varieties" (Rosner, 2004). The DNA alphabet consists of four major building blocks or base pairs which are connected to one another in long chains to assemble genetic words or genes; however, it's still important to acknowledge that not all DNA is made up of useful information: there is still non-coding DNA that doesn't transform into useful proteins and this is where changes can often crop up in the overall structure of DNA (Rosner, 2004). Changes can often occur in these regions because they make no contribution to the health or survival of the organism: "But compare the situation if a change occurs within an essential gene, preventing it from working properly; the organism will be strongly disadvantaged and probably not survive, effectively removing that altered gene from the population" (Rosner, 2004). It's also crucial to acknowledge that the abilities of forensic evidence are vast and that they are not simply relegated to merely fingerprinting or the standard methods of forensic pathology that are so commonly viewed on television crime dramas.

For example, one recent development in the world of forensic pathology has been the analysis of maggots. In Mexico, police investigator found an uncovered body that was so tremendously burned and unrecognizable, that the DNA could not be extracted for analysis: "Desperate to identify the body, a team of pathologists took a chance by analyzing the stomach contents of the maggots who were feasting on the corpse. Much to their surprise, they were able to extract the victim's DNA from the fly larvae -- and successfully identify the body" (Dvorsky, 2012). This was one of the first times when an actual legal investigation has attempted to use the gastrointestinal tract of a parasite and its contents as a means of extracting data. The investigators strongly suspected that the body of the woman was that of a woman who had gone missing two and a half month earlier (Dvorsky, 2012). Thus, using this as a starting point, the extracted DNA first worked to determine if the body was in fact that of a female and the following test tried to determine paternity: the scientists examined her maggot extracted DNA and compared it to that man suspected to be her father using a standard paternity test (Dvorsky, 2012). The test revealed a 99.7% chance that the two were father and daughter, thus verifying the woman's identity: "This is consequently the first reported case of taking human DNA from the gastrointestinal tract of maggots to identify a victim in a criminal case" (Dvorsky, 2012). The reason why this case is quite so fascinating is that it demonstrates the possibilities for forensic science in determining the truth and in uncovering the real facts when a crime is committed. In numerous cases, this type of forensic research can bring justice to the victims and peace to the families of the victims. There's a tremendous amount of good which can be done in this case.

Of course, not everyone embraces the capabilities and potential of the forensic sciences as heavily and wholeheartedly. One needs to acknowledge that from time to time the DNA from crime scene evidence is of poor quantity and badly preserved or extremely degraded: this means that a full DNA profile cannot be obtained (Norrgard, 2008). When less than 13 STR are scrutinized, the overall genotype frequency is much greater, making the likelihood of a match more random as well (Norrgard, 2008). What can make things even trickier is the fact that crime scene samples often have DNA from a range of sources, making the examination of the overall sources of DNA even more difficult (Norrgard, 2008).