Improving DNA Phenotyping for Forensics

Krystal Breslin describes the work that she’s doing at IUPUI to discover which SNPs determine eye, skin, and hair color in the hopes of making mug shots available to the police where eye witness testimony is not available.




My name is Krystal Breslin. I work at Indiana University Purdue University Indianapolis, or IUPUI in downtown Indianapolis. I work in Dr. Susan Walsh’s laboratory. It’s a DNA Phenotyping laboratory. We work on improving DNA phenotyping for the forensics platform.

For DNA phenotyping right now, currently what they use is a categorical system. So, they split it up into categories, like for example, eye color is brown eyes, blue eyes, that kind of thing, and then an intermediate color. So, basically, quantitative color prediction is giving an exact value of the prediction of the color.

So, rather than just giving a category, because my definition of blue eyes could be very different than your definition of blue eyes. So, we want to go and predict an actual RGB or HSB value. So, if you were to take Photoshop, for example, and zoom in on an eye, that exact value of what that color would be. So that’s what we’re looking to predict – that exact RGB or HSB value so that we can give an actual print out of what that eye color would be.

So, basically what we did in order to get the original genes that we looked at to give our categorical predictions of hair, eye, and skin color, we did a genome-wide association study or a GWAS, and from there, once we’ve determined the major genes that cause it, we look at the intermediate SNPs and genes that are located around the SNPs that we currently already look at in order to help find little things that tweak the colors that determine why a person has green eyes or why they have blue-green eyes as opposed to just straight blue eyes. So, looking at those intermediate genes that were not such big contributors before to figure out the intermediate colors.

So if you’re looking at just pigmentation, so like what we do, it’s very close. We can actually right now, we can give you a prediction of hair, eye and skin color – the same thing an eye witness would give you. So if someone were to say that someone committed a crime, they’d say the person had black hair, brown eyes, and medium complexion skin – we can do that kind of thing right now. In order to do the quantitative color, it’s a couple of years away.

We’re doing a lot of research right now to give an actual prediction, because what we want to do in the end is produce an actual mug shot of what the person looks like. So, we want to be able to hand police a printout and say this is who you’re looking for – this is what they look like. So, we’re in the process of trying to figure out exactly how to go about doing that. So, it’s going to take a little bit more research, but in the next one to two years, it probably should be possible. Depending on what other areas you’re looking at like age, balding – they’re a couple of years away. And then there are some things like height that we may never figure out. So, it just depends on what area you’re looking at, but in the realm of pigmentation prediction, completely separate from ancestry, it’s only a couple of years away.

Our model is very different from some of the others out there in that all of our work is completely independent from ancestry due to the add mixture in the United States and some people don’t express exactly what their ancestry is.