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The New Way Crime Scene Investigators Are Tracking Criminals


Crime scene DNA has traditionally been used to link a victim to a criminal. With a new process known as phenotyping, though, investigators are using that DNA to reverse engineer a profile of what the perpetrator might look like. Today on "Think," Lauren Silverman talked with National Geographic online science editor Erika Engelhaupt about phenotyping and other CSI innovations. The story, “Beyond a Reasonable Doubt” appears in the July issue of National Geographic magazine.

The KERA Interview

Erika Engelhaupt on …

… DNA phenotyping:

“The way DNA phenotyping works is you may have a sample that was left behind at a crime scene. You take that and you analyze the DNA and then you try to reconstruct the face of the killer by using associations that you’ve already developed. Using computer algorithms you can essentially take that piece of DNA and reconstruct what the face of that person would look like based on their DNA.”  

… the limitations of DNA phenotyping:

“Something like eye color we can say something with some degree of certainty about that, but you don’t know how old the person is based on the DNA, not with this kind of technology. You can really only sketch a person at a given age, but you don’t know how old they were when they committed the crime … you can’t tell things like, obviously, whether the person has a beard. They could have changed their hair … They’re a lot of things that people can do that would change their appearance that are not going to be encoded in their DNA.”

…. why DNA is more reliable than other methods:

“In the case of something like fingerprints or blood spatter analysis, clothing fibers, matching hairs, that requires a lot more on an expert looking at something and making a judgement call for themselves. They don’t have that kind of hard chemical analysis to go on. With DNA you’ve really got something that can be very highly repeatable, reproducible and that doesn’t require as much expert judgement or visually matching of one sample to another.”

… the CSI effect:

“As people have seen crime dramas on TV, of which I’m a fan. They’re a lot of fun to watch. But they can sometimes make it seem like it’s very easy to get this kind of really high tech really gotcha evidence, that really nails the case. In many cases, that’s just not how it works out in real life. It can be much more difficult.”