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.
These tests gave researchers four objective measures of pigmentation to compare with their DNA blueprint analyses. Scientists then used a statistical model developed by Robert Valenzuela, a fourth-year genetics graduate student, to ascertain the three best SNPs to explain each pigmentation variation.
The resulting analyses enabled forensic scientists to determine hair, eye and skin color through a DNA sample. With DNA blueprinting, analysts found they can learn a person's hair color with 70-percent certainty. Examining three separate nucleotides can also pinpoint the ratio of brown-black to yellow-red in a person's hair with 43-percent certainty. Researchers also found analysis could explain skin color variations with 50-percent certainty, and that eye color could be predicted with 76-percent certainty.
"The bottom line from these studies is that when we look at a relatively small number of single-nucleotide changes, for each of these traits, we can make a fairly accurate prediction as to what a person looks like," Brilliant explains.
Putting DNA blueprinting to use
DNA found at a crime scene will first be analyzed and put into CODIS to see if there is a match. This analysis looks at 13 changes in DNA for identification purposes but does not examine SNPs. To learn a person's physical characteristics, technicians would have to perform a second analysis using DNA blueprinting.
"This does not in any way replace the CODIS system, which is very important in determining whether a DNA sample came from a specific individual," Brilliant says. "It wouldn't be used to convict an offender. Rather it would be probative evidence, in other words a lead that would help officers hone in on a suspect."
What does this mean to law enforcement? Plenty, says William Watson, chairman of the Association of Forensic DNA Analysis and Administrators.
With nothing more than a DNA sample, investigators can paint a picture of a person's physical characteristics. "Like all genetic markers we've developed so far, this will turn out to be forensically significant," Watson says, "It will be useful as long as it's used with the understanding that investigators should not limit their suspect pool to only those people fitting those characteristics."
Watson, a fellow with the American Academy of Forensic Science, cautions investigators to remember that genetics are only half of the equation with environmental factors making up the other half. He also reminds that eye, skin and hair color are all things that can be altered. Suspects can change their eye color by wearing colored contacts; alter their skin color through bleaching, dyeing or even tanning; and change hair color by dyeing it.
Rande Matteson, associate professor of criminal justice at Florida's St. Leo University and veteran law enforcement officer of 32 years, calls the current research promising, but questions whether it will be applied. "From a law enforcement perspective, we don't use the tools we currently have," says the retired FBI Academy instructor and crime scene technician. "If someone could figure out how to take all this wonderful information and use it in a way that catches bad guys, my hat's off to them."
Watson agrees, stating this technique may be limited, proving useful when police lack eyewitnesses or leads from state, local or national databases. "If you've got nothing but some genetic evidence, this method may be employed," he says. "If you've got other information, you may want to focus on more traditional investigative tools first."
The current DNA backlog presents another major concern. Through data collected from a large, representative sampling of law enforcement agencies in the United States, a National Institute of Justice-funded study in 2003 revealed:
- The number of unanalyzed DNA cases reported by state and local crime laboratories is more than 57,000.
- Total crime cases with possible biological evidence, either still in the possession of local law enforcement or backlogged at forensic laboratories, is more than 500,000.
With forensic laboratories facing these kinds of challenges, Matteson questions how often DNA blueprinting might be reasonably applied. "Labs are very particular about what they analyze," he says. "And they've had tremendous cutbacks due to the economy, which will create an even larger backlog."
Watson predicts state and local forensic laboratories will not add new DNA markers to their testing capabilities any time soon. He cites mitochondrial DNA sequencing, which looks at DNA markers passed on to an individual by their mothers, as the primary reason for his belief. Only five private labs, four FBI labs and a handful of state labs currently perform these tests. "Because mitochondrial testing requires specialized handling, duplicate processing equipment and specialized training, most state and local labs submit that evidence to the FBI," he says.
Y-STR analysis, which examines DNA present on the Y chromosome of males, inherited only by males from their fathers, has also experienced similar difficulties. Watson says most state crime labs won't touch it. "They have enough standard testing to do without expanding into a whole other area of testing," he explains.
Cost will also be an issue, adds Matteson. "Agencies have a set budget and limited resources," he explains. "This testing will likely be very expensive."
While investigators and crime scene technicians are taught to collect anything and everything at a crime scene, Watson explains labs do not process all the evidence they receive. Rather they triage it, looking at the most critical evidence first. "They examine the samples most likely to be of probative value before looking at the others," he emphasizes. "If they don't find anything on those initial samples, they may go back and test everything. It comes down to money — the expense of the DNA kit, the number of analysts a lab has, and the number of cases they already have."
That being said, Watson predicts the University of Arizona's DNA blueprinting process may eventually be applied as mitochondrial or Y-STR testing is today — when all other avenues are exhausted. "When you've got genetic information but lack a suspect to compare it to — and it's a heinous serial case — that's when you expand to other types of DNA analysis," he explains.
One day, just as DNA ethnicity testing led investigators to search for a person of a specific ethnic makeup in the Baton Rouge case, DNA blueprinting may be used to pinpoint suspects' physical characteristics. DNA blueprinting may eventually become one more tool in the toolbox to help investigators solve crimes.
Ronnie Garrett recently left her position as the editorial director of Law Enforcement Technology for more than a decade to dedicate her time to her growing portrait photography business. She can be reached at firstname.lastname@example.org.
Single nucleotide polymorphism (SNP). A variation at a single site in DNA, which is the most frequent type of variation in the human genome.
Humane genome. This is stored on 23 chromosome pairs. The human genome has approximately four billion single nucleotides.
Mitochondrial DNA testing. This testing looks for the mitochondrial DNA females pass on to their offspring.
Y-STR testing. Y- STRs are Short Tandem Repeats (STRs) found on the male-specific Y chromosome. This testing looks at these STRs, passed on from a father to his male offspring.