Forensics: Where Tech Meets Yech
Keay Davidson, The San Francisco Chronicle
They're the unseen, underfunded wizards in the war against crime: forensic scientists.
Their scientific cunning and laboratory prowess can make the difference between success and failure in crime-fighting. Whether they're examining scratches on a sniper's bullets or collecting chemical residues from a terrorist bombing, forensic scientists play increasingly important roles in tracking down and convicting crooks.
Last week, a key clue in the arrest of the man suspected of being the East Coast sniper and his young associate was a fingerprint found on a gun magazine at an Alabama liquor store, the scene of a Sept. 21 robbery-slaying.
Police traced the fingerprint to John Lee Malvo, 17. On Thursday, Malvo was arrested in Maryland along with another suspect, John Allen Muhammad, 41.
But even high-tech scientific tools can't crack most crimes without at least two other ingredients: an alert citizenry and good, old-fashioned police work, forensic experts say.
Police in the terrorized Washington, D.C., area learned of their local shootings' link to the Alabama case thanks to a Virginia priest, who reported receiving a bizarre phone call from a man who mentioned the Alabama shooting.
Investigators believe the Alabama killing marked the beginning of a three-week, multistate shooting spree that killed 10 people and injured three.
The sniper case "illustrates the importance of old-fashioned police work and the importance of witnesses," said forensic scientist John DeHaan of Vallejo. "They had thousands of people combing the hills: Every time there was a shooting, they'd send barracks of guys out to search the grass" for clues.
LABS OVERWORKED, UNDERSTAFFED
That kind of labor-intensive toil dramatizes one of forensic scientists' current gripes: The latest spate of TV dramas ("CSI," "CSI: Miami") tends to glamorize their work, making it look higher tech and less grungy, bloody and downright ugly -- not to mention smelly -- than it really is.
"I've investigated homicides where I'm lying in pools of blood, trying to get photos (of crime scene clues) from the right angle. It is by far not glamorous," said forensic scientist James Crippin of Pueblo, Colo.
TV and films also create the impression that crime labs have huge budgets and rely solely on slick scientific gadgets such as mass spectrometers, lasers, computers and DNA analysis.
In reality, many of the nation's state, county and municipal crime labs are barely scraping by with small, overworked staffs, forensic scientists say.
The funding situation has worsened in recent years as legislators, captivated by the crime-fighting potential of DNA, have diverted dollars toward DNA labs and away from the more traditional tools of forensic science.
"The demand for DNA service has just gone crazy," and government agencies are "gutting the non-DNA laboratories," DeHaan said.
To date, DNA analysis has won plaudits for providing evidence that many people have been unjustly convicted, including some on death row. DeHaan, however, warned of an increasingly possible danger: that overreliance on DNA analysis might convict innocent people.
Suppose, for example, that a prosecutor's main evidence is human DNA in human hair, or on a cigarette butt, found at the crime scene. Such sophisticated-looking evidence might persuade a jury to convict the suspect.
DeHaan said: "Some investigators say, 'All I have to find is a single cigarette butt, determine whose DNA is in the saliva on the butt, and that's all I need.'
"But when was the butt dropped there? What is its relationship to the crime, if any? DNA alone can't answer those kinds of questions. To answer those questions requires other kinds of investigative work -- say, of shoe prints and fingerprints, which can get overlooked in the push to find DNA samples."
DNA analysis is the primary technological innovation in forensic science over the last decade. Older workhorses of forensic science include infrared scanners, which "see" features invisible to the naked eye; mass spectrometers, which identify chemical residues with extreme precision; and, of course, human fingerprints, which can be analyzed with lasers and compared using computers.
Computers can also be a useful tool. Sometimes, investigators use a computer to model a bomb explosion. This allows them to estimate how far explosive debris traveled and, thus, how much ground they must scour for clues.
Still, much forensic investigation remains firmly low-tech. For example, after a bombing, investigators wearing rubber gloves and knee pads walk or crawl shoulder to shoulder over the ground, seeking clues such as chemical residues that might allow them to identify the type of explosive.
"They're going very slow, on their hands and knees. They look like a bunch of ostriches with their butts stuck up in the air," Crippin said.
To find explosives residues, bullet fragments, blood droplets and other clues, investigators place clumps of dirt from the crime scene on a wire screen and sift through them, like prospectors panning for gold.
"If you get very tiny or no fragments, you can be fairly sure it's a high explosive," said Paul Dougherty, an independent consultant on forensic science who used to run the San Mateo County crime lab.
But in many explosions, "there's a surprising amount left -- the clockwork mechanism, wires, batteries," added Dougherty, who now operates DWM Laboratory in Ojai (Ventura County).
Two decades ago, Dougherty helped investigate a San Carlos bomber who placed an explosive in the driveway of his estranged girlfriend's home. The bomb detonated, injuring her father. Investigators traced the explosive to the bomber after locating a piece of residue: an electrical switch. The bomber had purchased the switch at a local store using a check that bounced.
Forensic science is a surprisingly small field. "There's not that many of us. There are probably less than 100 active explosives examiners in the United States," Crippin said.
DeHaan wanted to be a scientist from his earliest days in Chicago, when, following instructions in Scientific American's "Amateur Scientist" column, he built a miniature "atom smasher" in his basement.
Although he loves his work, he admits it has its dark moments. He'll never forget the time he sought clues by crawling through a tight, dark crawl space in a Union City home. The space was so tight that he was forced to squeeze past the rotting body of the victim: a slain young woman.
"There are certainly unpleasant scenes at crime scenes," DeHaan said with a low chuckle. "You're cold and wet, or you're hot, and you're out there examining blood spatter or shoveling ashes and thinking, 'Maybe Mom was right -- maybe I should have been an accountant.' "
CRIME-SCENE VISITS RARE
Ideally, a forensic scientist should visit the crime scene to get a feel for what happened, experts say.
Yet tight budgets make such visits a rarity. "Today, a lot of criminalists never see a crime scene because their laboratory workload is so great," DeHaan said.
Governmental agencies that fund crime-fighting tend to short-change crime labs in favor of more visible or glamorous crime-fighting tools: "more patrol officers on the street, more (police) cars, more helicopters, more investigative agents," DeHaan said.
A four-decade veteran of the field, Dougherty said he thinks prosecutors tend to go through waves of enthusiasm for different kinds of technology. He recalls how, a few decades ago, gas chromatographs were exciting new gadgets for forensic science. Prosecutors declared that "you had to use gas chromatographs for everything or you couldn't go to court" with your evidence. Later, mass spectrometers became the hot new tool. Now, it's DNA analysis.
"Sometimes," Dougherty said, "it's better just to sit back and look at the scene and see what the scene 'tells you.' . . . What does that broken window mean, or the broken bottle?"
In that regard, Dougherty likes to visit the scene before he talks to police investigators. That way, they won't accidentally prejudice his analysis.
"It's not unusual for the investigator to say, 'This is nothing more than an old-fashioned suicide' -- and it turns out to be a homicide," Dougherty said. "You've got to keep your mind open."
SOME OF THE FBI'S FORENSIC LABORATORY MILESTONES 1936 First use of polygraph in a criminal case 1937 First use of blood group testing 1972 Explosives unit created 1985 Shoe-print file computerized 1987 First identification of cocaine in hair 1988 First DNA analysis unit created 1992 Computer analysis team established 1996 Hazardous materials unit created for chemical, biological and nuclear terrorism incidents
-- ANATOMY OF A CRIME SCENE
Science is playing an increasingly important role in finding and convicting criminals, as police rely on an unprecedented arsenal of high-tech crime-fighting tools. But even these tools are useless if investigators aren't meticulous about the rather unglamorous job of gathering evidence at the scene of a crime.. BALLISTIC FORENSICS: Every rifled gun barrel leaves unique markings on bullets and cartridges. Gun-control advocates are pushing for a national database of these distinctive "ballistic fingerprints" to help solve crimes.. HIGH-TECH ANALYSIS: Evidence such as clothing fibers can be analyzed using techniques such as gas chromatography and mass spectrometry and compared with manufacturers' records. Unfortunately, the evidence is destroyed in the process. New techniques aim to solve that problem..
Sources: Bureau of Alcohol, Tobacco and Firearms; Federal Bureau of Investigation; Chronicle research
John Blanchard / The Chronicle E-mail Keay Davidson at firstname.lastname@example.org.