It’s a dream of DNA forensics: the ability to generate an accurate picture of a suspect from a DNA sample. How close are we, and how accurate will these pictures be? New DNA forensic techniques could soon let investigators learn a lot more from genetic samples.
In spite of media hype about artists creating computer-generated portraits from the DNA found in old chewing gum, we’re not quite ready to generate DNA-based police sketches. While these artist’s renderings are intriguing, there are two critical barriers to using DNA to create an accurate picture of a specific individual:
- Some traits are highly influenced by environmental factors. Childhood nutrition, diet and exercise patterns, tobacco and drug use, illness and sun exposure can have profound influences on traits such as height, body mass, skin tone, and wrinkling. And of course genes will tell us nothing about acquired traits such as scars, injuries, hair color changes or other body modifications.
- We haven’t yet found the genes for every possible physical trait. To build a picture of a specific face, our hypothetical drawing program would need to understand the relationship between genes and features such as the width of the nose, the shape of the cheekbones, the point of the chin and other traits such as earlobe attachment and widows peak. Most of these genes have not yet been identified.
We might not be able to generate a DNA-based police sketch yet, but there is still a lot of potential forensic value in DNA evidence. Here is what scientists can tell from a DNA sample today:
- Sex: DNA evidence will easily tell investigators whether their sample comes from a male or female suspect.
- Skin tone: Hair and eye color are inherited and easy to predict by looking at just 24 specific sites on the genome. The genes for melanin production influence skin tone and freckling, but these traits are also impacted by other genetic markers and by time spent in the sun. However, biogeographic ancestry (BGA) can give predictions about skin color and other aspects of appearance linked to specific ancestry.
- Height and weight: Predictions here won’t be exact due to strong environmental components, but DNA will give investigators some clues.
- Age: Our DNA is modified as we age in certain predictable ways. By looking at these markers investigators may be able to guess a suspect’s age within plus or minus five years.
- Whether or not someone has hair: Male pattern baldness is fairly well understood and can be predicted using DNA evidence. By combining these markers with age predictions, investigators can guess whether they are looking for someone gray, bald or with a head of youthful hair.
- Ancestry: Genes can’t tell us where a suspect lives now, but they can tell us where their ancestors originated. This can provide clues into ethnicity, which may predict the likelihood of certain physical traits.
Scientists at Battelle are pushing the boundaries of applied genomics to help investigators extract meaningful information out of DNA samples that do not product an exact match in existing DNA databases. Learn more about how Battelle ExactID helps DNA forensic scientists build a picture from DNA.