I'll Be Gone in the Dark(32)
Mary Hong was one of the criminalists tasked with concentrating on cold cases. Jim White took her aside. Fifteen years later, he hadn’t forgotten his old suspicion.
“Harrington,” he said. “Witthuhn.”
The names didn’t mean anything to Hong, who hadn’t worked at the lab at the time of the murders. White encouraged her to prioritize those two cases. “I always thought it was the same guy,” he told her.
A BRIEF, NONTECHNICAL EXPLANATION OF DNA TYPING MIGHT BE helpful. DNA, or deoxyribonucleic acid, is the molecular sequence that defines each human being as unique. Every cell in your body (except red blood cells) has a nucleus that contains your DNA. A forensic scientist working to develop a genetic profile will first extract available DNA from a biological sample—semen, blood, hair—then isolate, amplify, and analyze it. DNA consists of four repeating units, and it’s the precise sequence of the units that differentiates us from one another. Think of it as a human bar code. The numbers on the bar code represent genetic markers. In the
early days of DNA typing, only a few markers could be developed and analyzed. Today, there are thirteen standard CODIS markers. The likelihood of any two individuals (except identical twins) having the same human bar code is roughly one in a billion.
In late 1996, when Mary Hong went to retrieve the Harrington and Witthuhn rape kits from the Property Room, DNA typing was experiencing exciting changes. The traditional process, RFLP, was still used by the state database, but it required ample DNA that couldn’t be degraded in any way. It wasn’t ideal for cold cases. But the Orange County Crime Lab had recently integrated a new technique, PCR-STR (polymerase chain reaction with short tandem repeat analysis), which was much faster than RFLP and is the backbone of forensic testing today. The difference between RFLP and PCR-STR is like copying down numbers in longhand versus using a high-speed Xerox machine. PCR-STR worked particularly well for cold cases, in which DNA samples might be minuscule or degraded by time.
One of the first examples of forensic science solving a murder appears in a book called The Washing Away of Wrongs, published in 1247 by Song Ci, a Chinese coroner and detective. The author relates a story about a peasant found brutally hacked to death with a hand sickle. The local magistrate, unable to make headway in the investigation, calls for all the village men to assemble outside with their sickles; they’re instructed to place their sickles on the ground and then take a few steps back. The hot sun beats down. A buzz is heard. Metallic green flies descend in a chaotic swarm and then, as if collectively alerted, land on one sickle, crawling all over it as the other sickles lie undisturbed. The magistrate knew traces of blood and human tissue attract blowflies. The owner of the fly-covered sickle hung his head in shame. The case was solved.
Methods are no longer so rudimentary. Centrifuge and microscope have replaced insects. The unidentified male DNA that
was extracted from the Harrington and Witthuhn rape kits was subjected to the crime lab’s most sensitive tools: restriction enzymes, fluorescent dyes, thermal cyclers. But forensic science advancements are really just about finding the latest way to draw a blowfly to a bloody sickle. The goal is the same as it was in thirteenth-century rural China: cellular certainty establishing guilt.
Hong appeared in Jim White’s doorway. He was at his desk.
“Harrington,” she said. “Witthuhn.”
He looked up expectantly. Criminalists like Hong and White are methodical people. They have to be. Their work is always being torn apart by defense attorneys in court. They often keep their conclusions broad (“blunt object”), which can cause tension with cops, who accuse them of being too self-defensively cautious. Cops and criminalists need each other but are temperamentally very different. Cops thrive on action. They are knee jigglers with paper-strewn desks they avoid. They want to be out there. Bad-guy behavior they know as muscle memory; if they approach a guy and he abruptly turns to the right, for instance, he’s probably concealing a gun. They know which drug leaves burn marks on fingerprints (crack) and about how long someone can survive without a pulse (four minutes.) They slog through chaos inured to bullshit and squalor. The job inflicts lacerations. In turn, the cop becomes lacerating. At his most lacerating, when the darkness has gone through him like dye through water, he’ll be called upon to comfort the parents of a dead girl. For some cops, the pivot from chaos to comfort becomes harder and harder to do, and they abandon the compassion part altogether.
Criminalists orbit the chaos from a latex-sheathed remove. The crime lab is arid and rigorously maintained. There’s no hard-edged banter. Cops wrestle up close with life’s messiness; criminalists quantify it. But they’re also human beings. Details from cases they worked stay with them. Patty Harrington’s baby blanket, for
example. Even as an adult she slept with the little white blanket every night, rubbing its silk edges for security. The baby blanket was found between her and Keith.
“Same guy,” Hong said.
Jim White allowed himself a smile before getting back to work.
A FEW WEEKS LATER, AS 1996 CAME TO A CLOSE, HONG WAS AT her desk scanning an Excel spreadsheet on her computer. The spreadsheet was a compilation of the twenty or so unsolved cases in which DNA profiles had been successfully developed. The chart cross-referenced case numbers and victims’ names with the profiles, which consisted of five PCR loci, or markers, that were then in use for typing. For example, under the marker “THO1” you might see the result “8, 7” and so forth. Hong knew the Harrington and Witthuhn profiles matched. But as her eyes swept over the spreadsheet, another profile stopped her cold. She read over the sequence several times and compared it to Harrington and Witthuhn to be certain. She wasn’t imagining it. It was the same.