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DNA testing has dramatically altered criminal investigations, and it turns out that scientists are just getting started.

NPR's Dina Temple-Raston begins a series of reports on high-tech forensics with a visit to the FBI crime lab in Virginia.

(Soundbite of robotic arm)

DINA TEMPLE-RASTON: Hear that? That's the sound of a small revolution.

(Soundbite of robotic arm)

TEMPLE-RASTON: That whirring noise is a robotic arm skimming along a long tray of test tubes. Each contains a small blood sample, and the machine is bathing the samples in a sort of chemical detergent that breaks the human cells open.

The DNA releases inside the test tube and settles to the bottom of the tube like sediment in a bottle of wine. That sediment is then fed into another instrument, which reads its genetic code to be included in a database that may one day contain DNA samples from every single one of this country's federal offenders.

That kind of database would have taken years to put together if human technicians had to do it. The revolution is this robot. It can do 500 samples a day, many more than a human ever could.

Ms. JENNIFER LUTTMAN (FBI): We still use people to find the DNA...

TEMPLE-RASTON: Jennifer Luttman runs the convicted offender program at the lab.

Ms. LUTTMAN: ...to look for the stains, to test if it's blood, to test if it's semen, to cut out the stains, because they need to see how much is there, and that's all based on - on experience.

TEMPLE-RASTON: But Luttman says there are parts of the DNA database-building process that can be done more efficiently by machines. And that's new.

Ms. LUTTMAN: Once, though, the DNA is extracted in a purified form, we then are starting to do all of the casework aspects on robotics, because that then is a very consistent process. And so we're putting robots into place to allow the humans to concentrate on the areas that they - are most needed.

TEMPLE-RASTON: And where humans are needed most is at the crime scene trying to discover forensic evidence that television programs like "CSI" imply any good investigator should be able to find.

Mitchell Holland is a member of the forensic science department at Penn State. He thinks juries are raising the bar on evidence.

Dr. MITCHELL HOLLAND (Penn State): The data is suggesting that interviews of jurors are such that they're saying if they'd only done DNA I would have convicted, when they probably had enough in the case to already convict.

TEMPLE-RASTON: Expectations are rising because the science is getting better. Not so long ago, forensic experts needed a sample the size of a nickel for processing. Now it just needs to be the size of a pin prick. So cases that were unsolvable just a decade ago are now ripe for reopening.

(Soundbite of centrifuges)

TEMPLE-RASTON: That's the sound of centrifuges running. This crime lab in rural Virginia is where experts tug clues from a different kind of DNA. It's called mitochondrial DNA. Your regular DNA, found in blood and semen, is known as nuclear DNA. If you think of that as being part of the yolk of an egg, mitochondrial DNA is in the white.

The downside to mitochondrial DNA is that it isn't as useful for identification, but the upside is that it doesn't break down as quickly. And that makes it vitally important to so-called cold cases.

Alice Eisenberg is the head of the FBI's Mitochondrial DNA Analysis Lab, where experts can find clues and evidence that's been sitting around for years.

Ms. ALICE EISENBERG (FBI): Cold cases are our meat and potatoes, if you will. They typically include bones that have been found several years ago and have never been identified as belonging to a certain individual, or it can also include hair samples that have been stored with other evidence for many years and no one ever was able to perform DNA analysis on them until we came along with our mitochondrial DNA technology.

TEMPLE-RASTON: The newest wrinkle in that technology is a rather innocuous-looking machine called a mass spectrometer. The actual machine is not very big. It's about the length of a kitchen counter and a little over 5 feet tall. Inside, you can see little robotic arms moving trays around a series of short towers.

(Soundbite of machine)

TEMPLE-RASTON: A mass spectrometer is basically a fancy scale that weighs individual molecules. To now, law enforcement has used it to identify chemicals like accelerants around suspicious fires. The FBI lab is the first to use it to measure mitochondrial DNA in crime work. The idea is to separate out the DNA's component parts by weight.

Here's why that's important. If you have an event like the World Trade Center attack in which remains end up comingled, it's hard to tell which DNA is which. Weighing the DNA in the mass spectrometer fixes that problem because it's able to use weights to identify different fragments of the DNA.

Les McCurdy is a forensic examiner in the DNA analysis lab. He likes to use a coin analogy.

Mr. LES McCURDY (FBI): You have pennies, nickels, dimes and quarters. Each one of those coins will have a different weight. So if I have a pocketful of 10 coins and I put that on a very sensitive scale, we can whittle down that number and determine how many pennies, how many nickels, how many dimes and how many quarters. It's the same type of thing that we're doing with mitochondrial DNA with this instrument.

TEMPLE-RASTON: Essentially, the machine helps them shake out and identify several individuals from a DNA mixture. The robot picks up a plate, reads a bar code on its side, cleans the DNA and then using magnetic beads separates it out so it can be put in the mass spectrometer for weighing. A computer then records the various weights and DNA combinations.

Mr. McCURDY: I got to tell you, as a scientist, this is very exciting. Not only is it technologically advanced and it's cutting edge, but it's also going to have a tremendous application. And I think it's really going to open up all new types of evidence to us, all new types of cases, and I think it's going to have a huge impact on how we can assist different investigations.

TEMPLE-RASTON: This new mass spectrometer technology is still in its infancy, but it is part of a larger program to expand the use of DNA, and even people outside the FBI, like Penn State's Mitchell Holland, see new uses for DNA.

Dr. HOLLAND: The power of DNA is what is beginning to emerge in that by using it just like a fingerprint, you can actually get a match to a previously convicted offender, and that's really exciting.

TEMPLE-RASTON: The question is whether these new DNA advances will raise the forensics bar even higher, with jurors expecting science to wring doubt out of their deliberations. The FBI is quick to say that new DNA science doesn't just assign guilt. Almost a third of their DNA work goes towards exonerating suspects. Because of that, they say, these DNA advances are good for everyone.

Dina Temple-Raston, NPR News, Washington.

INSKEEP: Later today, Dina Temple-Raston looks at audio forensics. Just how do they know those Osama bin Laden tapes are real?

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