90.9 WBUR - Boston's NPR news station

Interactive DNA Testing Procedure
Requires the Macromedia Flash plugin


DNA and the Science of Truth


Ed Blake's Forensic Science Assoc.

Learn more about the science of DNA, from NOVA

CODIS, the FBI's DNA Profile Bank

The movie and the book, Jurassic Park, tell the story of a brilliant -- if misguided -- scientist who builds a modern-day theme park populated with real dinosaurs. In the story, scientists recover tiny strands of dinosaur DNA from fossilized mosquitoes that have been preserved for tens of thousands of years in amber. They isolate the DNA, copy it and construct perfect dinosaur-DNA profiles - and then, real dinosaurs. The idea that we can resurrect dinosaurs may be science fiction, but the science that inspired the story is real. A process called polymerase chain reaction - or PCR - is allowing scientists to reach back in time and resurrect not dinosaurs, but truth.

Truth is often unearthed, and science always revered, in the laboratory of Dr. Edward Blake, just outside San Francisco. The first thing you notice just outside his office is a miniature scale that weighs two small cards: one of the cards reads, "The opinions of forensic scientists," and it appears to be much heavier than the other card, which reads: "The opinions of lawyers." When prompted to comment on the display, Blake's gravelly voice cracks into a laugh. "Most of us believe that the opinions of lawyers aren't worth very much," he says, "because lawyers believe that under the umbrella of advocacy they can lie through their teeth." Blake's eyes are already ablaze with indignation as he practically pants with passion. "And they're not even ashamed to admit it."

Blake is a man of strong opinions. He's also one of the nation's most respected forensic scientists, and the first to work with PCR, the technique that inspired "Jurassic Park," and in 1985, revolutionized DNA testing. "We're at the level now," explains Blake, "where we have the holy grail of genetic discrimination." Blake says this revolution in genetic discrimination was like replacing a pair of blurry glasses to study the stars with the Hubble telescope.

The exoneration of Earl Washington shows just how powerful modern DNA-testing is. A police investigation, a confession and a jury sentenced Washington to die. DNA analysis set him free. Peter Neufeld of the innocence Project calls DNA "the gold standard of Innocence" because it is much more reliable than all the other kinds of traditional evidence - such as eyewitness testimony, hair analysis, or statements from jailhouse informers. "This is scientific evidence," says Neufeld, "that can prove identity conclusively."

But some people worry that the reverence for science in general, and DNA in particular, can go too far. Gary Close, the County prosecutor in Culpepper, Virginia, where Earl Washington was tried and convicted, worries that respect for science has been elevated to "almost religious faith." Close does not dispute that DNA offers investigators a powerful tool, "but criminal cases don't rest solely on DNA," he says, "but on a wide range of evidence." In the case of Earl Washington, Close believes Washington's confession outweighed the DNA evidence.

Some, including the forensic scientist, Edward Blake, say that represents the stubborn refusal of public officials to admit they made a mistake and sentenced an innocent man to death. "The only objective evidence [in the case] is the sexual assault evidence," argues Blake, "and that evidence has spoken as loudly as any evidence could speak." And in this case, Blake says, the evidence clearly demonstrated Washington's innocence and the state's error.

But on the broader issue of DNA analysis as a final finder of truth, Blake is more cautious. "It helps establishes a fact," he says, "and that's it." And fact, he argues, doesn't always lead to the truth. Consider the trial of O.J. Simpson in which prosecutors presented a wealth of credible DNA blood-evidence that linked Simpson to the murder of his wife and her companion. Simpson's defense team, which included Blake as an advisor, couldn't challenge the DNA science, so they challenged how it was interpreted; and accused police and prosecutors of tainting the evidence - even planting it. Blake says the blood evidence in the Simpson case was clearly an important component. "But when the entirety of the case in compromised by the way the government conducts its affairs," he says, "reasonable doubt raises its ugly head." In other words, the case showed that in the hands of skillful lawyers like Barry Sheck and Peter Neufeld, DNA is just one piece of evidence among many.

Since the mid-1980s, DNA testing has led to a number of spectacular exonerations of the falsely convicted. But as a prosecutorial tool it has led to many more arrests and convictions. At the Virginia State crime lab, which houses the nation's first and largest DNA databank, Dr. Paul Ferrara says his staff averages almost two "cold hits" a day - when they match DNA evidence from a crime scene with the profiles stored in their computers. "It happens daily now," Ferrara says with a good deal of pride.
During our visit, Ferrara takes us into a "codis room," where forensic scientist Bob Scanlon uses a computer to work on an unsolved rape case from 1996 that hadn't been subjected to modern DNA testing until now. Sperm from the victim produced to a DNA-profile that's now being compared to nearly 200,000 profiles in the databank. Scanlon watches rows of numbers fill his screen. Then, as Ferrara leans over his shoulder, Scanlon points to one set of figures that are flashing. "That's probably a good hit," he says. This cold hit will provide a name of a suspect, as well as probable cause that will permit police to seek an arrest. Ferrara says cold hits like this also often lead to quick convictions. "When confronted with a strong case that includes DNA," he says, "a lot of people recognize they're better off taking a plea than fighting it."

The state of Virginia is expanding its DNA databank to make it even more effective. Under a new law, the state plans to take saliva-based DNA not only from convicts, but from everyone arrested for a violent crime. Jerry Kilgore, Virginia's Attorney General who sponsored the new DNA law, says it will enlarge the data bank and give law enforcement officials a chance to catch violent offenders more quickly. "It's a public safety issue," according to Kilgore, who says the new law will provide "a better opportunity to determine if we have a serial killer, or if we have someone who has committed crimes over and over again."

Home | Death Row Stories | Science of DNA | Law & Politics
Inside Out | Credits | WBUR