Mia Gale was taught that hair shafts don’t contain nuclear DNA worth pursuing. Her research produced full STR profiles from them anyway.
Rootless hairs are common at crime scenes, but the nuclear DNA in a hair shaft is scarce, highly degraded, and mostly lost by standard extraction kits built for larger fragments. Her research optimized a widely available extraction method to capture the smaller fragments those kits discard, then used it to process 130 hair samples. Some of the resulting STR profiles were complete enough to generate random match probabilities as rare as 1 in 3.5 octillion.
Read on for the day her data finally moved in the right direction, what a hair shaft can still tell you when every other lead is gone, and why she wants forensic scientists to stop discounting rootless hair.
What's the story behind your research — what made you curious about this specific question in the first place?
When I learned about the research projects at GW, I was especially drawn to those involving complex samples. The idea of generating STR profiles from hair caught my attention, as I had previously been taught that hair shafts contained no nuclear DNA. The project was definitely ambitious, which made it even more rewarding when we started seeing results.
Describe your research to someone who hasn't worked in your specific area.
The majority of hairs collected from crime scenes do not contain a substantial root. While the remaining hair shaft does contain nuclear DNA, it is present in much lower quantities and is highly degraded. Commercial forensic DNA extraction kits are not optimized to recover fragments under 100 base pairs, resulting in the loss of small DNA fragments during the extraction process. Ancient DNA extraction methods, which are designed for degraded DNA, are generally time consuming and laborious, making them impractical for the typical forensic DNA lab to implement. The purpose of my research was to optimize a DNA extraction method that increases the capture of small fragments, while remaining practical and possible to implement in crime labs by using tools which are commonly available. We then processed 130 hair samples with our optimized method and amplified the extracts with the smallest possible STR amplicons commercially available to increase STR allele recovery from hair shafts.
What's the moment in your research that surprised you most — a result you didn't expect, a method that didn't behave, or a finding that made you rethink everything?
Optimizing our method was a tedious process, and each time it didn’t work was disappointing. The most surprising day was when we found the correct combination of changes to capture a greater quantity of DNA fragments under 100 base pairs. We were waiting for a graph that represented the fragment sizes we captured to shift to the left, indicating we captured more small fragments. Let’s just say I saw a lot of versions of the graph not moving, so the day we finally saw a shift was the best surprise!
What does a good day in your research actually look like — and what does a hard one look like?
A good day in research is having a full, uninterrupted day to conduct experiments that all go according to plan while listening to good music. A hard day in the lab is when you have a cutoff time, such as a class, and suddenly no experiments are behaving and everything is going overtime. I’ve had a mix of both kinds of days!
What impact do you hope your research will have on the field?
I hope that my research shows the field that hair shafts are a viable and underutilized source of nuclear DNA in casework. Particularly when other evidence sources have been exhausted, a hair shaft could unlock new information.
If someone walks away from your poster remembering one thing, what do you want it to be?
I would want them to remember that hair shafts can contain fragments of DNA long enough to amplify STRs and not to discount rootless hairs!