The Reaches (and Limits) of Forensics

Detectives and sniffing dogs are largely gone from the leaf-strewn slope in Rock Creek Park where the remains of 24-year-old Chandra Levy were found. But some forensic experts say it's possible clues could remain on the forest floor.

Authorities in Washington, D.C., are faced with a puzzle. They know the former intern was killed. But they don't know how she died and they admit they may never find out exactly what caused her death. What they really want to discover is who killed her. Forensics may lead them to the answers.

For example, forensic botanists could analyze vegetation growing around the crime scene to determine how long Levy's body had been in the Washington park. Trace-evidence specialists could glean information from single strands of hair, fibers and bits of dust and pollen.

The intern had been missing for 13 months before the grim discovery in Rock Creek Park. All that was found of Levy's remains were a collection of bones, some clothing and personal effects. If authorities had found the body soon after her death, forensic entomologists could have combined data on weather and the age and kind of insects present on a body — mainly blowflies — in complicated calculations to determine a time of death.

• Interactive: Forensic Tools

As the hit television series CSI: Crime Scene Investigation has portrayed, forensic science offers a myriad of high-tech methods for analyzing clues. But as the technology behind forensic science advances, experts caution forensic scientists must take extra care to ensure they scour crime scenes for all possible clues, and that forensic analysis is not overplayed in the courtroom.

Herb MacDonell, founder of the Bloodstain Evidence Institute in Corning, N.Y., cautions forensic deduction can seem elementary, but "in forensic science, nothing is simple."

Every Action Leaves a Trace

French scientist Edmond Locard declared in the early 1900s that every violent action leaves a trace and even the most minute traces can help solve crimes. It was on this foundation that Locard opened one of the first laboratories dedicated to the field of forensic science in 1910.

Two years later, Locard found a killer by analyzing material underneath a female victim's fingernails.

Other renowned sleuths added their own contributions. In the mid-1800s, Mathieu Orfila published one of the earliest papers about the detection of poison in the blood. Henry Faulds, a Scottish physician working in Tokyo in 1880, was among the first to suggest that fingerprints could be used to identify suspects. And Calvin Goddard developed ways to determine if a bullet was fired from a suspect's gun in the early 1900s.

Sir Arthur Conan Doyle's fictional character Sherlock Holmes popularized the field when he applied some of the cutting-edge methods of his time including developing theories of serology, fingerprinting and firearm identification.

Since then forensic scientists have gained better tools to glean even more information from tiny clues. But while forensic science is helpful in the lab, Peter DeForest, a crime scene investigator and trace analysis expert at John Jay College of Criminal Justice in New York, argues forensic scientists should have a greater presence at the early end of investigations — during the search for clues at crime scenes.

"You need someone with a scientific background assessing the entirety of the physical evidence," said DeForest. "It often takes scientific training to recognize a clue."

Missed Blood on Nicole Simpson’s Back

DeForest says the West Coast is further along in adding scientists to the ranks of detectives released first to crime scenes. It was in Los Angeles, after all, that opened the first forensic lab in the United States in 1923. The East Coast, he says, has been somewhat slower to change.

Nonetheless, it was in Los Angeles where one of the more infamous examples of overlooked evidence took place, during the investigation into the slayings of Nicole Brown Simpson and Ronald Goldman in 1994.

Photos of Simpson's body revealed blood spattered on her back that analysts later concluded must have originated from someone else — perhaps her killer. But investigators failed to take a genetic sample of the blood before turning the victim on her back and contaminating any possible samples.

Other times it has taken a forensic scientist to realize a clue has value.

As he offered a tour through John Jay's forensic training laboratories, packed with instruments, including gas chromatographs (used to separate traces of chemicals from sediment or blood), spectographs (measures light emitted by a sample) and comparison microscopes (microscopes that provide magnified images of two samples at once), DeForest recalled one case where tiny strands of fiber helped prosecute a suspect.

In 1993, the strangled body of 30-year-old Russian immigrant Vladimir Makhno was found dumped in a bush area in the remote area of York, Ontario, Canada. DeForest got a phone call. Could he identify some orange fibers found on Makhno's body?

Using spectrograph analysis and comparison microscopes, DeForest was able to match the fibers with remnants of a carpet found in a suspect's home. Ironically, it wasn't the prosecution who had thought to call DeForest about the fibers. It was the defense.

"I guess the prosecution didn't think the fibers were that important," said DeForest. "The laboratory didn't realize the significance of what they had."

Defense attorneys thought the fibers would absolve their client, since preliminary tests showed the suspect's carpet was made of two kinds of fibers, not one. But when DeForest tested the carpet himself, he learned that it only shed the fiber type that was found on Makhno's body.

"You have to learn how to ask the right questions as well as find the right answers," explained DeForest.

‘Junk Science’

Although scientific evidence is often overlooked, sometimes it can also be overplayed. A 1993 Supreme Court decision, known as the Daubert ruling, stipulates that courtroom justices prompt questions about the scientific sturdiness of evidence. But the problem of so-called junk science still lingers.

MacDonell is the leading expert on "reading" blood spatter at crime scenes. He has testified in such high-profile cases as the assassinations of Robert F. Kennedy and Martin Luther King Jr., as well as the O.J. Simpson case.

He also helps instruct others in the science every year at his Bloodstain Evidence Institute. At the clinic, students literally throw human blood around (old pints of it are bought from the Red Cross) to understand how it falls and splatters.

While he's confident that most of his students finish his clinic better equipped to interpret crime scenes, he says some have become overconfident.

"I think bloodstain analysis is being used and abused more and more," he said. "Of my students, there are about five Frankensteins."

Part of the problem is the science can seem deceivingly simple. The basic premise of bloodstain analysis is a droplet's size reveals how much energy was applied, its shape suggests the direction of its source and its distribution reveals how far away from a surface blood was splattered.

"You have to take them all together," MacDonell said. "It sounds simple, but if you haven't had a lot of experience, you can make a lot of mistakes."

Other fields of forensic analysis are also facing increased scrutiny.

The ability of researchers to identify a suspect through fingerprints was challenged by a federal judge in January. U.S. District Court Judge Louis H. Pollak ruled that fingerprints lifted from crime scenes cannot meet standards of scientific scrutiny established by the Supreme Court since most detected prints are smeared and incomplete. Pollak said examiners cannot testify at a trial that a suspect's fingerprints "match" those found at a crime scene.

Michael Saks, a law professor at Arizona State University, says he thinks the use of bite marks left on victims as identifying evidence is also on shaky ground. He says recent tests show the method averages an error rate of about 62 percent — much higher than misidentification rates in fingerprint tests or handwriting analyses.

"I keep waiting to see a big challenge in court," he said.

Search Continues

In the Levy case, authorities have ideas about how she died — that she was strangled or suffocated — but they have no conclusions.

"Was it a sexual assault? An attack by a stranger, by someone she knew? All of these are possibilities," Metropolitan Police Chief Charles Ramsey said last week.

Investigators are searching for a monogrammed ring and a bracelet that Levy may have been wearing at the time of her death. The hope is merchants at a local pawn shop might have interacted with her killer. They're also analyzing remnants of her clothing, including spandex leggings that were found with knots tied in them, suggesting she may have been sexually assaulted.

Other clues may yet emerge.

Katherine Ramsland, a professor of forensic psychology at DeSales University in Bethlehem, Pa., pointed out in a recent Philadelphia Inquirer column that Levy's clothing could host blood or DNA specimens that belong to someone else. And fibers or foreign hairs may still be clinging to her shoes or clothes — especially if her body was brought to the location by a car and wrapped in a blanket or carpet.

As Ramsland wrote, "It is grim, difficult work, but one good thing is that modern forensic science has many techniques to call on."