The analysis of hair has been a “hairy” situation for forensic science over the years. Traditionally, scientists examined hair under a microscope and then testified that it either matched or did not match hair found at a crime scene. However, this type of analysis is no longer considered scientifically valid and has been put to rest as part of a forensic science overhaul that began in 2009 with the now-famous National Academy of Sciences report.
Even so, hair left at a crime scene is not completely useless. Microscopic analysis can still be used to rule suspects out, and scientists are actively researching full-proof ways to incorporate hair analysis back into forensic science, as well as the legal system. Proteomics-based research has been the most successful in identifying individuals.
In 2016, for example, researchers at Lawrence Livermore National Laboratory developed a biological identification method that exploits the information encoded in proteins of human hair. In hair, protein sequences vary slightly from person to person, and because they are coded in our genes, they are permanent features of our identity. The technique to extract proteins from hair samples required multiple steps comprising soaking, grinding and chemical treatments. Proteins were lost during each sample prep step, meaning the original sample had to be substantial if results were expected. Protocol required roughly 10 mg or about 100 5-cm strands of hair—an amount not likely to be left behind at a crime scene.
Now, scientists at the National Institute of Standards and Technology (NIST) have found a way around this limitation. Their new method dissolves human hair proteins without destroying them, requiring only a single 5-cm strand of hair. The glaring difference is the number of steps involved—the NIST method only requires one step, which allows more protein to be recovered from a given amount of hair. Once the proteins are extracted, they can be analyzed using standard proteomic analysis methods, the most popular being different forms of mass spectrometry.
Additional research
In a related project, the same NIST researchers identified 12 new genetically determined variations in human hair. While they still need to be verified with genetic studies, the more verified points of comparison forensic scientists have, the more precise the results. Scientifically driven, precise results are the kind that get closer to the courtroom.
NIST research chemist Meghan Burke, who is also the co-author of the paper published in the Journal of Forensic Sciences, said the research team hopes to identify additional variations in hair proteins. They are also working with geneticists at NIST to map keratin variations to the genetic sequences that give rise to them. That will allow comparisons not only of one hair to another, but of a hair to a DNA sample, such as linking hair at one crime scene to a bloodstain at another.