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Advances in science help bring criminals to justice

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Posted: Friday, June 27, 2003 10:00 pm

"DNA tests free man convicted of two killings."

"DNA links victim to Louisiana slaying suspect."

"Remains tested for DNA of Saddam."

As science and technology advance, the term "DNA" is appearing in more and more headlines around the world. The three-letter acronym that stands for deoxyribonucleic acid - a small part of a cell - has almost become a household word. Each person has a unique combination of microscopic bands that join to form DNA.

But it is only in recent years that those bands have been used to link people to crimes - or exonerate them.

When John Yoshida began working for the state's Department of Justice 21 years ago, the only chance investigators had was to look at enzymes.

cold_dna_snodgrass_030628.jpg
Criminalist Nicole Snodgrass records the weight and descriptions of a drug in the drug lab at the Central Valley Forensic Laboratory for the Department of Justice.(Jennifer M. Howell/News-Sentinel)

In best-case scenarios, a suspect was narrowed to one out of 100, or one out of 200.

Now, at the department's forensics lab in Ripon, where Yoshida serves as director, things have changed.

In the very first DNA case the lab handled, scientists narrowed the suspect down to one in 4 quintillion people - or a 4 followed by 18 zeros.

"The possibility of him being the suspect was more than the number of people that are on this earth," Yoshida said.

In San Joaquin County, the detective in charge of the cold case unit has been sifting through more than 100 old homicide cases, looking for evidence that has never before been tested for DNA.

"I'm crossing my fingers, hoping we get a hit," Detective John Basalto said of a case in which criminologists hope to examine blood from a 21-year-old killing in which a Stockton woman was found stabbed to death.

Basalto is hoping that, mixed in with the victim's blood, scientists will find a bit of the suspect's blood. With modern technology, they could possibly separate the two blood samples, extract the DNA and link it to a person.

Such a process is much more quickly said than done.

The forensics lab

At the DOJ's Bureau of Forensic Sciences Central Valley Laboratory, which serves five counties, criminologists spend their days trying to solve criminal cases ranging from drug lab busts to assaults and homicides.

The building opened a little more than a year ago, and employees work on some 300 drug lab cases each year, Yoshida said. Individual drug cases number about 6,000 a year.

"This lab started with about four people five years ago, and now I have 25 people under me and we're still backed up," Yoshida said.

The blend-in, 32,000-square-foot building has few markings on it to indicate that it's a crime lab, and a skate park sits almost next door to the $12 million building.

But no one can get beyond the lobby without an employee identification card, or without being accompanied by an employee.

The card allows an employee entrance past a gray, 400-pound, bulletproof door, then down white hallways and around corners. The card is also required for access to other restricted areas in the lab.

One room is dedicated to the Scanning Electron Microscope, which is worth $350,000.

The machine can magnify objects up to 250,000 times - far beyond a standard high school or college microscope.

"You can take a fly's eye and look into each prism of its eye," Yoshida said.

A bullet casing magnified 70 times can reveal a marking that is unique to each firearm, allowing investigators to link the casing to a gun.

In one rape-homicide case, Yoshida said, the microscope was used to magnify a single hair from the victim's body. It revealed bits of paint that could not be seen to the naked eye, and the paint was matched to a suspect.

"It's a whole different way of looking at something," Yoshida said.

Lab experts look at nearly every aspect of a case - including recreating homicide scenes - but DNA has increasingly become the most reliable piece of evidence.

With a perfect DNA match, the only court challenges are whether the evidence was handled properly and the scientists were competent, Yoshida said.

Finding DNA evidence

Four full-time analysts can handle about eight DNA cases a month, said Assistant Laboratory Director Katy Ciula. And that's if a case doesn't take more time and have additional complications.

The DNA process begins with the evidence. The case investigator works with a lab criminologist, looking at the general case and what might be useful. Sometimes, it's easy. Sometimes, it's not.

"Blood on a nice, white shirt is easy to see. You put blood splatter on a pair of dark jeans and it's a lot harder," Ciula said.

There are three basic ways to find biological material, she explained. The easiest way is to simply look at the evidence. Sometimes it can be found with special lighting. And in some cases, investigators feel the evidence, looking for a spot that feels different - a stiff place on fabric, for example.

That's just the preliminary part of the DNA investigation. On hour-long television shows, the next step would simply be a matter of running the evidence through a machine that would immediately separate the DNA and match it to a suspect.

cold_dna_lawson_030628.jpg
Jennai Lawson, senior criminalist for the Department of Justice at the Central Valley Forensic Laboratory in Ripon, works with DNA samples.(Jennifer M. Howell/News-Sentinel)

In real life, it's a long, scientific process that must be handled with the utmost of care so that no evidence is contaminated.

In the Serology Room used to store blood and tissue evidence, five white freezers are carefully monitored 24 hours a day to make sure that the evidence inside is not contaminated.

Once evidence is taken into a DNA room, technicians only leave with a disk containing the analysis, rather than moving the DNA and risking contamination, Yoshida said.

They wear gloves at all times, and most people are not even allowed into the room.

Extracting DNA

"The first thing you have to do is get the DNA out of the nucleus of the cells," Ciula said.

That process alone takes all night, as the cell is broken down to remove proteins and the cell wall. The remains are put in a centrifuge, and the scientist is left with about two microscopic drops of clear liquid.

"Then you have to find out how much DNA you have pulled out," Ciula said, referring to it as the quantitative step.

Dealing in size increments of nanograms (a billionth of a gram) and picograms (a trillionth of a gram), the analysts react the DNA with chemicals so that it gives off a fluorescence, Ciula explained.

The bands in DNA are then revealed, and the darkness of the bands is compared to a standard. If the bands are dark enough, the analyst has enough DNA.

The next step is called the amplification process, in which the DNA is multiplied until the analysts have enough.

"It's like a cake mix in that a cake requires three eggs to make a cake. There's a little bit of leeway as to the size of the eggs, but you need three eggs," Ciula said.

That process takes about four hours, not counting the set-up time.

From there, the DNA sample is run through a process in which particles are separated in an electric field, called "capillary electrophoresis," Ciula said.

Once again, that process takes time, as each sample takes about 30 minutes.

In a relatively simple case involving an assault with one victim and one suspect, the analysts run about 10 and 15 samples, Ciula said. That would take an additional five hours, at minimum, so the process is generally done overnight.

Then the analysts actually look at the data.

"You have to interpret all the peaks and make sure everything worked correctly. That can take a day to get through the data or it can take a couple of weeks," Ciula said.

Throughout the process, documentation is the most involved procedure. Every step is documented, and another technician checks the work. The entire case then goes through an administrative review before it is ever released.

In the meantime, lab technicians are constantly checking the equipment, monitoring it and making sure nothing has malfunctioned.

Once the DNA is inspected and a profile is built, it still must be matched to a person. The state now has thousands of DNA samples from all convicted felons, but getting DNA samples from suspects requires a warrant.

In several of Basalto's cases, DNA is still circulating through computer files as he waits and hopes to get a "hit," meaning someone with matching DNA has been identified.

Basalto recently got just such a "hit," but wouldn't say which of more than 100 cases it was in order to prevent any possible compromise of the investigation. Whether the "hit" will lead down another road or to another dead end remains to be seen.

"The information is there. It's just a matter of finding it," Yoshida said.


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