Forensic biologist Silvana Tridico was puzzled by pubic hair.
Specifically, pubic hair samples donated by two volunteers.
She had just finished analyzing the bacteria stuck to the hair of seven people. If each hair sample carried unique mixes of bacteria, Tridico reasoned, investigators might have a new tool to help identify crime suspects. Hair bacteria, like fingerprints, could offer a forensic link between criminals and the bits of bodily debris they left behind.
But two of the hair samples held nearly identical microbe populations. “I thought I’d made a mistake,” Tridico says. She repeated the analysis, and still, the hairs’ bacteria matched. One explanation came to mind.
“I said to my partner, ‘I think they’ve had sex.’ ”
Tridico was right. Two of the study’s participants had, in fact, had sex 18 hours before snipping off strands of their hair for Tridico’s analysis. Their bacteria apparently mingled so much, she says, that their microbial medleys became indistinguishable. Since the telltale traces lingered for so many hours — even after the volunteers had showered — Tridico thinks the technique has the potential to match sex offenders to their victims.
“I’m so pumped,” says Tridico, of Murdoch University in Perth, Australia. “I really think it’s got traction.”
CSI Dollhouse
In the mid-1900s, Frances Glessner Lee built detailed miniature crime scenes, “Nutshell Studies of Unexplained Death,” to help police learn to identify important evidence (see main image above). The dioramas are on display in Baltimore at the Office of the Chief Medical Examiner.
Though still in early stages, her technique and other advances signal the rumblings of a seismic shift in the forensics field. One day, tiny microbes could hand investigators big clues. Bacteria shed from people’s hair, skin and footprints, or fungi hidden in specks of dust, could help place suspects at the scene of a crime. And just a whiff of odor clinging to a fingernail or seeping from a dead body could help investigators track a missing person — or corpse.
As new techniques gain their scientific footing, researchers are also shoring up classic forensic tools that have taken recent high-publicity hits. Some of the most time-honored techniques, such as fingerprint analysis, have been resting on rickety foundations. In the last few years, researchers have taken a closer look at forensic science’s tarnished old hide. Bit by bit, they’re tugging it into the 21st century.
Traces of trouble
If justice is a woman clutching sword and scales, then forensic science is a sprawling beast, with a hodgepodge of tools stuffed in its fists.
These tools target almost every mark a person can leave behind: fingerprints, blood spatters, handwriting, DNA, hair and more. Each trace represents a little shred of history that might help investigators piece together a picture of the past.
But not all forensic science disciplines are created equal. Some, such as fingerprint analysis, are steeped in more than a century of tradition but not a lot of data. Seasoned experts train apprentices in the craft, and examiners’ opinions can carry too much weight.
Criminal forensics’ shortcomings drew international attention in 2004, when the FBI bungled the investigation of the Madrid train bombings. The bureau’s lab matched a single smudged fingerprint on a plastic bag to an Oregon attorney named Brandon Mayfield — an innocent man. Mayfield spent two weeks in jail before the Spanish National Police identified an Algerian man as the fingerprint’s actual source. The U.S. government formally apologized to Mayfield in 2006 and agreed to pay him $2 million.
The misidentification of Mayfield sparked renewed scrutiny of forensic techniques, says John Butler, a forensic DNA scientist at the National Institute of Standards and Technology in Gaithersburg, Md. “It really woke people up.”
Soon after, a National Academies panel poked into forensics’ scientific nooks and crannies. In 2009 it released a damning report. The story was grim: Deep cracks ran through several forensic bedrocks — especially those based on expert interpretations of patterns.
