When Victor Vega was accused of stabbing a man multiple times, prosecutors had help putting him behind bars.
Using an innovative DNA testing computer program called TrueAllele, investigators were able to differentiate between the victim's blood and Vega's skin cells, both of which were on a knife and sheath found at Vega's residence.
Vega was convicted Aug. 22 of attempted murder with premeditation for the benefit of a criminal street gang, as well as other assault and gang charges. He faces 25 years to life in prison.
It was the second time Kern County prosecutors had used TrueAllele to gain convictions. In a third case, the defense tried unsuccessfully to use DNA from TrueAllele on behalf of their clients. A fourth case -- the so-called east Bakersfield rapist -- has not been tried yet.
Kern Regional Crime Lab bought TrueAllele in October after receiving a grant of more than $200,000 from the National Institute of Justice.
Kevin Miller, director of the crime lab, said it is fairly easy to differentiate between two people's DNA on a piece of evidence, but when it is three or more people's DNA it becomes challenging. In Vega's case, TrueAllele helped identify the probability the DNA belonged to him and his victim.
TrueAllele helps identify not only the DNA but also assesses the probability it matches the person in question.
"I've been a DNA case worker for 20-plus years," Miller said. "I've been at the bench, testified, done DNA case work all over country. This is a very innovative approach."
Like other DNA testing, samples used for TrueAllele's comparison can be collected with a simple cheek swab. The program looks at the DNA more accurately than an expert could do by eye, the method previously used by labs. It has not, however, shortened the crime lab's 124-day turn-around for results on identifying DNA samples, Miller said.
The computer program's name is a play on "allele," one of two or more versions of a gene. People inherit two alleles for each gene, one from each parent.
Dr. Mark Perlin, creator of TrueAllele, said in an interview that when more than two people's DNA is found on evidence, it becomes a much more complex pattern, making it harder for a human DNA analyst to interpret.
To narrow down possibilities, TrueAllele looks at all the different ways the sample could have provided the genotypes seen, Perlin said. A genotype is the makeup of a person's genetics.
The computer program is based on a probability model. It compares the genotypes against as many people as needed, whether it's one or 100,000, Perlin said.
In his experience, Perlin said human analysts would not be able to do that on such a large scale and therefore the evidence often isn't used in court.
"From labs we speak with, about half of mixture data is not reported out," Perlin said. "(But) most of the mixture data does not get entered into this system."
The DNA tested can come from bodily fluids or from "touch DNA" such as skin cells on weapons, clothing or countertops. Additionally, the program helps simplify DNA studies in a way jury members can understand to help either tie a defendant to the crime or rule out as a suspect.
To help a jury understand, the probability model and principals of DNA testing would be explained to them by attorneys on the case or in testimony. Jurors would then be shown the likelihood of whether the DNA found matches or did not.
Kern County Deputy District Attorney Richard Choi prosecuted the Vega case and thought the DNA on the knife was a necessary piece of evidence in the trial.
"Without it we couldn't have secured a conviction," Choi said.
The three times TrueAllele was used in Kern County were the first in a California court or anywhere west of the Mississippi River. Most of the program's use has been on the East Coast.
"The forensic community can be slow to adopt new methods," Perlin said. "Practitioners and crime labs will look at (some DNA) and say it's too complex to interpret. And the idea of using a computer to make that easier is (unusual)."
TrueAllele has assisted in some large-scale investigations.
In September 2006, Cybergenetics, the company that owns TrueAllele, won a contract to reanalyze and reinterpret DNA found from World Trade Center victims' remains in the 9/11 terrorist attacks, to help identify the victims.
In that case, there were 18,000 victim remains and 2,700 missing people's DNA tested. TrueAllele made about 50 million comparisons to try and make identifications.
Perlin said he does not know how many of those were matches, but the information was given to the Office of the Chief Medical Examiner in New York City. Cybergenetics was not told how much of its information was used.
Despite not knowing the results, he remains optimistic about the potential TrueAllele has to work on crimes in the future.
"Technology can take you to somewhere the human eye can't see," Perlin said.