Foon Rhee

At Sacramento crime lab, ‘CSI’ meets real life

Criminalist Nikki Sewell tries to extract DNA from a jacket in a robbery case at Sacramento County’s forensic sciences laboratory.
Criminalist Nikki Sewell tries to extract DNA from a jacket in a robbery case at Sacramento County’s forensic sciences laboratory. Sacramento Bee file

Editor’s note: This article was originally published on June 23, 2013.

Jill Spriggs is showing off her highly trained staff and the expensive equipment they use to dissect evidence from crime scenes and help solve cases.

The highest-profile part of Sacramento County’s forensic sciences laboratory, however, is off limits. It’s where criminalists create DNA profiles – and where every precaution is taken to prevent contamination. The afternoon Spriggs gave a tour, Nikki Sewell was trying to extract DNA from a jacket in a robbery case and Angel Shaw was processing a rape kit. In another lab, Leslie Poole was hoping to match bullet cartridges from a series of shootings after swabbing a gun for DNA.


On Monday mornings, Spriggs finds out if any DNA profiles from unsolved crimes sent the previous week match any in the state database of people arrested or convicted of serious crimes. Typically, there are two or three hits a month. “If it’s a big case, we get excited,” she says.

While it isn’t as quick and easy as “CSI” makes it look on TV, DNA can be an amazing tool, catching those who have been literally getting away with murder – and freeing those who have been wrongly convicted. That is, if it’s all working as designed. That’s what we’re counting on as more and more Americans are forced to submit DNA samples that are kept in ever-larger databases.

DNA evidence, however, is not foolproof.

A series of high-profile failures – including a death penalty case in Virginia and a rape in Houston – put innocent people in prison. At most crime scenes, investigators don’t find enough usable DNA. When evidence is available, samples sometimes sit waiting to be analyzed because of backlogs at understaffed labs.

That on-the-ground reality was glossed over by the U.S. Supreme Court ruling this month clearing the way for police to routinely take DNA samples – without probable cause – from those merely arrested for serious crimes.

While the justices focused on constitutional protections against unreasonable search and seizure, much more attention ought to be paid to the risks of people being falsely accused and convicted, says William C. Thompson, a professor of criminology, law and society at University of California, Irvine. One of the nation’s foremost experts on DNA testing, he and other academics filed a brief urging the court to consider the error issue.

DNA is generally reliable, but “reliable and perfect are not the same thing,” Thompson says. As databases grow, so does the risk for false or coincidental matches. Because police, prosecutors and juries put so much trust into DNA evidence and because the crimes may be many years ago, it can be very difficult for an accused person to prove they didn’t do it.

In a chapter he wrote for a book published in February by Harvard University Press, Thompson predicts that to thwart investigators, devious criminals will not only avoid leaving their DNA but will plant someone else’s.

Still, the trend is strongly toward more testing. As DNA technology has improved and won broader acceptance, California’s dragnet has expanded dramatically, and is now wider than in many other states.

It started with sex offenders in 1984, then during the 1990s extended to those convicted of violent crimes. In 2004, California voters passed Proposition 69, which mandated DNA testing for those convicted of all felonies, violent or not. It also required that DNA be taken from anyone merely arrested for any felony, starting on Jan. 1, 2009.

With nearly 2.2 million profiles, California has the world’s fourth largest DNA database, behind only the United Kingdom, the FBI and China. About 473,000 profiles – more than 20 percent – are from people who have been arrested, but not convicted.

To hear state officials tell it, it’s working fabulously. The number of “hits” with profiles from unsolved crimes has jumped from about 180 a month to 430. The rate of cases helped by DNA matches has nearly doubled from 35 percent to 68 percent – a total of more than 18,500 investigations.

California’s DNA collection program, however, is under challenge in state and federal courts. Critics say the state is taking genetic information from too many people who aren’t violent criminals and is keeping their profiles too long.

Often before charges are even filed, authorities collect and analyze samples from those arrested for nonviolent felonies such as drunken driving and writing bad checks. If charges are dropped or you’re acquitted, you need a judge’s approval to get your DNA profile erased from the state database.

Thompson says that while California’s DNA labs are generally good, they are still susceptible to mistakes. While technology is improved, it’s still only as good as the people using it. Even without scientific misconduct and fraud, he says, there are many sources for unintentional errors -- contamination when genetic material gets mixed in from another sample or from lab technicians, mislabeling of samples, or flaws in interpreting or reporting test results.

“I’m not saying that mistakes happen all the time, but they do happen,” Thompson told me.

The state says it has strict procedures to stop and spot errors, most notably second tests by both the state lab and local lab to confirm any matches. Still, mistakes slip through. Last month in San Jose, murder charges were dropped against a man whose DNA was supposedly found under the fingernails of a slain millionaire after lawyers showed the suspect was in a hospital at the time of the killing.

At the Sacramento lab, a criminalist resigned in 2006 after problems with his work – in particular a Rancho Cordova rape case in which he created a substandard DNA profile that was wrongly matched with one in the state database. Officials removed the profile and checked other cases he had handled. The District Attorney’s Office says no other cases were compromised.

Spriggs, who came to Sacramento last September from overseeing the state DNA labs, says a similar mistake is much less likely now. Technicians clean their work areas before starting each case. They wear surgical masks, gloves and lab coats, and don different ones in the airtight room where DNA profiles are completed.

But Spriggs says there is no 100 percent guarantee. “Contamination will happen at any DNA lab,” she says. The solution is to catch it – through layers of quality control safeguards – before a flawed profile is used.

Not surprisingly, officials much prefer to talk about the DNA lab’s successes, like the 2010 convictions in two cold-case murders in Sacramento or the life sentence in November for three brutal home invasions in Natomas.

The technology is advancing so much that real life may soon catch up with TV. Sacramento’s lab just received a $135,000 piece of equipment, bought with a federal grant to reduce backlogs, which can analyze 24 samples at a time, up from 16. Soon, new field kits will allow checks of 23 genetic markers, up from 15, making matches that much more certain.

In the next five to 10 years, there could be a suitcase-sized “rapid DNA” device that, from a cheek swab, can put together a profile within 90 minutes to be checked against databases. So it’s possible that someone who is arrested could be linked to a cold case before they are booked into jail.

That’s what you would call quick justice – if it’s accurate.

Foon Rhee: 916-321-1913, @foonrhee

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