When Pam Kinamore left work on a Friday evening, July 12, 2002, she never came home.
Four days later a Louisiana state worker discovered her body near the Baton Rouge Whiskey Bay Bridge. An autopsy revealed she had died from gash wounds to her neck, and that her murder bore similarities to several other murders that occurred in the same area months earlier.
A serial killer was clearly at work. An FBI profile pegged the killer as a white man, aged 25 to 35. After months of telling the public they sought a white man in the slayings of five area women, authorities announced they were searching for a light-skinned, black man in his late 20s or early 30s.
A revolutionary new DNA test relying on Single Nucleotide Polymorphism (SNP) was one of the reasons behind law enforcement's about-face. A Sarasota, Fla., forensics lab studied DNA from the crime scenes and concluded the suspect was likely 80-percent African-American and 15-percent Native American. In other words, the Baton Rouge killer was probably not white at all. This information led to a break in the case after months of frustration, and helped police arrest the killer, Derrick Todd Lee, just four days later.
DNA ethnicity testing has already helped authorities pinpoint a suspect's race. Now research from the University of Arizona has revealed specific changes in a person's DNA blueprint can also explain variations in hair, skin and eye color.
"With this new analysis, we have a basis for a physical description from an individual's DNA," says Murray Brilliant, Lindholm professor of Mammalian Genetics at the University of Arizona College of Medicine Department of Pediatrics.
The new testing technique arose out of a study where University of Arizona researchers were examining the genes responsible for human albinism. As part of the research, scientists studied a large population to learn whether the genetic variations they'd identified as potentially contributing to albinism occurred in the same frequency among people with normal pigmentation.
"We learned individuals have different variations and these variations were not always associated with albinism," Brilliant says. "However, these variations did change the protein encoded by the gene in specific ways."
Scientists then questioned whether these subtle SNP changes might also be tied to changes in pigmentation. Researchers compiled a list of all known changes in these genes and began evaluating them. The human genome has approximately four billion such nucleotides, which are the pieces that make up a person's genetics. These blueprints determine each person's individuality and can tell us the likelihood of developing heart disease, diabetes or cancer, or having light or dark eyes, skin and hair.
The team of researchers, led by Brilliant, examined the DNA blueprints of 800 university students. They had participants fill out a questionnaire that asked things like: What color eyes do you have? What color hair? Was your hair lighter as a child? What information is on your driver's license?
Researchers then collected DNA samples and approximately 300 snippets of hair from each participant for analysis. They chemically analyzed the hair samples looking at total pigmentation and the rate of brown-black melanin (eumelanin) and yellow-red melanin (pheomelanin). "Most people have both kinds of melanin in their hair," Brilliant explains. A bit more yellow-red and a person might be a strawberry blonde, while more brown-black might make them a redhead, and even more brown-black might make them a brunette.
A reflectometer measured light reflected off the skin on the underside of the subject's arm, where skin is less likely to be affected by the sun. Lighter skin is more reflective than darker skin, which is more absorbent, Brilliant explains. A standard eye chart, used to match eye color for artificial eyes, determined the color of each subject's eyes.