We all love a good crime story. We particularly love it when we can’t see it coming: the subtle tire marks left on the road match the culprit’s car, or the victim’s bite marks line up with the perpetrator’s molars. It begs the question, though: can these cases hold up as forensic evidence in a real court room? Forensic science is exactly that –- a science. The tools associated with this discipline uphold to the high standards of the scientific method.
Other than DNA testing, many forensic testing methods are actually not scientifically validated, and thus unreliable. Yet they have been given in testimonies to support (or prosecute) a defendant. According to the US-based Innocence Project, DNA testing (which is scientifically valid, but can often yield unruly results) has uncovered 225 wrongful convictions. Almost half of these DNA exonerations were due to fickle forensic science. Fortunately for you, we’ve mapped out three ways how forensic science can actually fail.
1. Forensics in the follicle: a hair-y situation
In some homicide investigations, forensic analysts will use hair as evidence. For instance, they may claim that the hairs from a crime scene “match” the hair of the defendant. Yet hair analyses itself has yet to be accepted as a valid tool by the scientific community. Comparing hair samples via microscopes are proven to be error-prone and subjective. In fact, 24% of the cases later exonerated by DNA analysis were due to testimonies based on hair analysis as evidence.
2. What’s your type? The science of serology
A vast bulk – about 27% – of the cases exonerated by DNA testing was due to improper use of blood typing, which is also called serology. This forensic technique, which has yet to be properly scientifically validated, involves comparing the blood type of samples found at the crime scene. Before the advent of DNA-testing in the 80s, forensic investigators commonly used serology to help determine the source of blood, semen or other types of body fluids found as evidence. For instance, forensic analysts use serology to find the blood type in a rape collection kit.
The sample, however, can easily contain fluids from both the culprit and the victim. Moreover, the victim’s blood type can hide the blood type of the perpetrator, so it would be quite challenging to know their true blood type. Also, a blood type ‘match’ is a probability, not an absolute — so they would need to explain that the person committing the crime shares the same blood time with a portion of the population.
3. The other side: mistakes and misconduct
While many times it’s the science at fault, other times it’s the scientist’s blunder. It’s often unintended, and due to lack of training and resources. While we like to think that most forensic scientists adhere to stringent standards when analyzing a crime case, there have been incidences of misconduct.
University of Virginia School of Law Professor, Brandon Garrett, researches wrongful convictions in the US. In one study, he analyzed invalid testimonies that were later shown to be false due to DNA testing. In his study, published in the Virginia Law Review, Garrett chronicled cases in which forensic analysts fabricated test results, hid parts of the test results or reported results when in fact no testing had been done. This type of misconduct led to multiple wrongful convictions in the US.
Like all disciplines, forensics is far from infallible. Awareness of this fact will help keep the discipline in check, and ensure its experts continually work towards making it better.
Your Turn: Are there any other aspects of forensic science which isn’t as accurate as we’ve been led to believe? Anxious to share more about any of the identified shortcomings we’ve listed within the discipline? Let us know in the comments. We’d love to hear from you.