The Eliminator: DNA Tech For Detectives

Every investigation is a process of elimination. When a crime has been committed it is an investigator’s job to narrow the field of possible suspects until he or she can build a case against an individual or a group of individuals.

For some cases it’s easy to eliminate everybody else and focus on one suspect. For example, when you find a woman murdered and her friends and relatives say her ex-boyfriend was a violent man, it’s pretty easy to determine the focus of your investigation. You still have to build a case, but the violent ex-boyfriend quickly becomes a person of interest.

Other cases are not so easy. A body is found in an alley, the victim of a random crime. You don’t have a suspect; so, theoretically, your murderer could be quite literally anyone. Now the process of elimination becomes long and tedious.

But that may not be true much longer. A new and controversial technology developed by Sarasota, Fla.-based DNAPrint Genomics is providing investigators with a way to quickly eliminate entire populations of potential suspects.

DNAPrint Genomics’ new DNAWitness technology allows you to use DNA evidence to learn the physical characteristics and basic appearance of a suspect even when you can’t match the DNA to a specific individual in the CODIS database. DNAWitness lets you include or exclude certain persons from an investigation based on their ancestry. Since its introduction to the forensic community in 2003, DNAWitness has been used around the world by such agencies as the FBI, the Royal Canadian Mounted Police, and Scotland Yard to help investigators solve crimes more quickly.

Core Technology

DNAPrint Genomics was founded in late 1999 as a pharmacogenomics company, researching the role genetics plays in drug metabolism. During this research an amazing discovery was made; the genetic differences among various racial populations were measurable by examining a genetic marker called a single nucleotide polymorphism (SNP, pronounced “snip”). The researchers examined more than 25,000 SNPs that were thought to measure ancestry from four population groups: European, East Asian, Native American, and Sub-Saharan African, and the information was used to develop DNAWitness.

The latest version of DNAWitness (version 2.5) analyzes 176 SNPs that are Ancestry Information Markers (AIMs), determined by testing hundreds of individuals with deep genealogical histories in the four population groups. Sub-Saharan samples came from Nigeria, East Asian samples from China and Japan, Native American samples from Mexico, and European samples from Western Europe.

When a person’s DNA is tested with DNAWitness, his or her AIMs are compared with the information in the database to determine his or her genetic percentages of the four population groups. The result is the DNA donor’s biogeographical ancestry (BGA). To give investigators a basic idea of what this individual might look like, his or her BGA result is compared to a database of more than 1,000 samples.

Of course, the idea of using DNA evidence to trace the ancestry of an individual to a general geographical sample raises some red flags. Critics say that the test can lead to racial profiling by law enforcement agencies.

Zach Gaskin, DNAPrint Genomics’ forensic technical director, responds that critics of DNAWitness are not fully informed on the technology. Gaskin argues that DNAWitness is not a race test because race is a social construct. The test deals with biology and heredity and ignores geopolitical boundaries. He says the test is blind to racial bias, prejudice, or bigotry, and simply looks at DNA and compares the results to reference populations.

Benefits for Investigators

New forensic technology must provide meaningful, useful information to investigators. And DNAWitness does just that.

Consider, for example, a sexual assault and homicide where the perpetrator left behind genetic material. The investigation identified 100 possible suspects: 15 Caucasian males, 30 African-American males, 25 males of Mexican origin, and 30 East Asian males.

A sample of the DNA was submitted for testing. Within one to two weeks, DNAPrint Genomics completed the testing and generated a report listing the race characteristics of the suspect. In this case, he was determined to be primarily European. The report concluded that, based on the suspect’s BGA, he exhibited characteristics of a white man. The result was that 85 of the 100 suspects are eliminated at this point, allowing detectives to concentrate their valuable time on the most likely perpetrators.

DNAWitness is not limited to testing suspect DNA; it’s also useful for victim identification. In November 2003 a woman’s dismembered body was found in a wooded area of Frederick County, Virginia. The woman’s head was missing and investigators were having a difficult time identifying the victim.

Police submitted her genetic material to DNAPrint. The results showed the victim was 85 percent East Asian, not Hispanic, as investigators previously believed.

Sending a Sample

Investigators interested in submitting a sample should first contact DNAPrint Genomics to discuss the case. This type of testing is most useful in situations where the suspect’s or victim’s DNA profile is in CODIS but the identity of the person is still unknown. However, it’s still useful if the suspect’s or victim’s profile has never been entered into CODIS. Note: DNAWitness is a separate test, so your local or state laboratory will still enter the standard STR DNA profile into CODIS.

The company accepts any type of biological evidence for testing, but the best-case scenario is if your local or state crime lab has already performed DNA testing on the evidence. A very small portion (about 10 nanograms) of this extracted DNA can be tested using the DNAWitness technology.

One of the reasons that DNAWitness works on such a small sample is that the test is very sensitive. It even works well on degraded DNA. DNAPrint Genomics has tested genetic material that only gave six of the 13 STR loci necessary for CODIS. The same sample yielded 150 of the 176 possible SNPs, and the result was a usable BGA profile.

DNAPrint requires that an agency send evidence to be tested via an overnight carrier with a tracking system. This ensures a solid chain of custody.

The submitting agency completes a request for service form that includes basic information about the agency, case number, contact person, etc. This form also includes specific questions about the submitted samples that should be filled out by laboratory personnel.

DNAWitness 2.5 testing costs $1,000 per sample. But demand is high. So high, in fact, that DNAPrint Genomics has contracted with the Lynn Peavey Company and ReliaGene Technologies to help expedite the process.

The Lee Case

Look at the following case study and you will see why business is booming at DNAPrint Genomics.

Between 1998 and 2003 many women in southern Louisiana were living in fear. A serial killer, dubbed the “Baton Rouge Killer,” was raping and strangling women, dumping their bodies in rivers or the woods.

Police followed leads and spent exhaustive hours searching for the killer. As public outcry to catch the killer intensified in August 2002, a multi-agency homicide task force was formed. More than 40 investigators from various agencies, including the FBI, the Louisiana State Police, the Baton Rouge Police Department, and the East Baton Rouge Parish Sheriff’s Office were involved in the manhunt.

The killer left behind genetic material at many of the crime scenes. Investigators compared the unknown suspect’s DNA and learned that seven murders were linked by DNA, while he was suspected of at least six more murders.

Eyewitness testimony led investigators to believe the suspect was a white male. And FBI experts performed a criminal investigative analysis (commonly called profiling) on all the evidence and developed a profile of the killer that agreed with the eyewitnesses. The killer was definitely a white man between 25 and 35 years of age. Acting on that information, investigators asked hundreds of white males to voluntarily provide buccal swabs for DNA comparison. But after 18 months of work the task force was no closer to catching the killer.

The investigators were perplexed. Then in February 2003, a fortuitous meeting occurred between Louisiana State Crime Lab personnel and representatives from DNAPrint Genomics at the American Academy of Forensic Science conference.

They discussed a new technology that might shed some light on the killer’s identity, and the State Crime Lab submitted a small sample of DNA from one of the killings for the DNAWitness test. The results were a revelation for investigators. DNAWitness results showed the murderer had a BGA of 85% Sub-Saharan African and 15% Native American, which is indicative of someone exhibiting features that are common to someone of African-American descent.

In March 2003, the task force told the public not to concentrate on the composite sketches of the Caucasian male suspect. They stated that the suspect could be of any race or appearance, and a new composite sketch was released showing a light-complexioned black man.

Revitalized with this new information, the task force personnel shifted their focus and, after two months of solid detective work, the investigators acquired a DNA sample from a West Feliciana Parish man named Derrick Todd Lee. Days later, laboratory results indicated Lee was an exact match with the DNA found at the crime scenes.

An arrest warrant was issued on May 26, 2003. Lee was arrested the following day by the Atlanta Police Department, after he fled Louisiana. Convicted of multiple murders, he is currently awaiting execution on Louisiana’s death row.

A Cold Case

DNAWitness is also useful in cold case investigations as well. At my agency, the Boulder Police Department, we are using the technology in an unsolved murder from 1997.
In that year, Susannah Chase, a 23-year-old University of Colorado student was walking home late at night when she was brutally beaten and left to die in a downtown alley. Hundreds of people were interviewed and almost 100 DNA samples were collected and compared to seminal fluid found at the crime scene.

The trail went cold. Then, early last year, we learned about DNAPrint Genomics and its predictive DNA test. We sent in a sample to see what DNAWitness could tell us about our suspect.

What we learned was well worth the $1,000 processing fee. The test results indicated that the DNA contributor might have appearance traits commonly associated with Hispanic males. Just as important, the results excluded East Asian, Sub-Saharan African, and European males from contributing the DNA. The story ran in the newspaper and generated a number of new investigative leads that are still being investigated.

Future of the Technology

DNAPrint Genomics continues to conduct cutting-edge research, hoping to discover more genetic traits locked in human DNA. In fact, the company just introduced a new test called Retinome, which infers eye color from someone’s DNA. Retinome is now available to forensic markets at a cost of $500 per sample.

The company is also expanding DNAWitness to include additional population groups for biogeographical testing, including persons of Middle Eastern, Indo-European, and South Asian descent. Forensic validation studies are ongoing and these groups should be added to DNAWitness soon.

Beyond expanding its DNAWitness population database, DNAPrint Genomics is working to broaden the focus of the technology. Gaskin thinks the next level might be determining specific facial characteristics from DNA, including such traits as nose shape and whether someone’s ear lobes are attached or detached.

DNAWitness is the first predictive forensic DNA test in the world. Unlike traditional DNA testing, the test results don’t point to one specific person but infer what someone might look like based on their BGA. It is a powerful investigative tool, helping detectives save valuable time by narrowing their search to the persons that likely committed the crime.

This technology can also limit the burden placed on already overworked forensic DNA laboratories. Investigators don’t need to make blanket submissions anymore, but can reduce lab requests because detectives are able to exclude individuals based on their BGA. Gaskin is happy to speak with law enforcement agencies that are thinking about using this technology.

David Spraggs is an investigator and firearms instructor with the Boulder (Colo.) Police Department. He also teaches forensic photography and crime scene investigation.