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March|April 2004
A Course of Inaction By John C. Coffee Jr.
Expiration Date By Jessica Sachs
The Big Fix By Daniel A. Nathan
Readers Respond: Justice Blackmun

Expiration Date

No scientist knows more about time of death than Bill Bass.

By Jessica Sachs

TIME OF DEATH. IT CAN MAKE OR BREAK THE ALIBI of a homicide suspect, help assign a name to a body decomposed beyond recognition, and even determine who inherits what when a fire, car collision, or some other tragedy kills a cluster of family members with disparate wills.

But the inability to determine the time since death, known as the postmortem interval, has bedeviled our legal system. Even TV's fictional Quincy, M.E., avoided trying to fix time of death, instead spending episode after episode cleverly teasing out cause of death for his storied corpses.

In real life, cause of death is usually obvious to a medical examiner and, for that matter, to most every officer responding to a homicide. Bullets leave blackened pits; a knife, gaping wounds; and blunt objects, internal injuries and fractured skulls. Even poisons leave clear signatures—child's play for a coroner with access to toxicology screens. But if the body contains a trusty internal clock, some biochemical display that freezes the time when the power goes out, it has yet to be found.

Not that legions haven't searched for it. More than two centuries of earnest scientific research have tried to forge better clocks based on rigor, algor, and livor mortis—the progressive phenomena of postmortem muscle stiffening, body cooling, and blood pooling. But instead of honing time-of-death estimates, this research has revealed their vagaries. Two bodies that reached death within minutes of each other can, and frequently do, show marked differences in postmortem time markers. Even the method of testing eye potassium levels, which was recently hailed as the new benchmark for pinpointing time of death, has fallen into disrepute, following autopsies that showed occasional differences in levels in the left and right eye of the same cadaver.

Nonetheless, many less experienced medical examiners hazard more confident determinations in cases of suspected murder than their science can support. The temptation is understandable, given the badgering they face from prosecutors and investigators who believe that they know how a victim was killed and just need an M.E. to help "prove" it. Even in the couple of days after death, however, the most careful experts are now loath to make anything other than barn-door estimates of the postmortem interval, with a "give or take" of no less than 6 to 12 hours.

And the longer a body is dead, the harder it is to figure out when its owner died. In their book The Estimation of Time Since Death in the Early Postmortem Period, the world-renowned experts Claus Henssge and Bernard Knight warn pathologists to surrender any pretensions of doing science beyond the first 24 to 48 hours after death.

The medico-legal twilight zone of that period—once the body has reached room temperature, rigor has melted away, and blood pooling has stopped—remained unexplored until the early 1980s, when the forensic anthropologist Bill Bass established "the Body Farm" on a patch of derelict land behind the University of Tennessee Medical Center in Knoxville. Since then, forensic scientists have studied the decay of more than 500 bodies, recording differences across a range of seasonal temperatures and humidities and looking at diverse homicide scenarios in which victims' bodies were buried, exposed, submerged, burned, or (as in one case) left to decompose in a closed car trunk.

From this macabre plot came some of the first systematic findings of forensic entomology (which determines time of death from the estimated age of bugs on bodies), as well as the so-new-it's-not-yet-named discipline of estimating time of death from the chemical breakdown of body fluids leaching from a decomposing corpse.

As Bass and his co-author Jon Jefferson make clear in their book Death's Acre, the inspiration for the Tennessee research facility sprang from the legendary inaccuracy of one of Bass's own estimates. On a late December morning in 1977, the new owners of an antebellum mansion in Williamson County, Tenn., reported a disturbance in the Civil War-era cemetery at the back of their property. When sheriff's deputies arrived, they discovered what appeared to be a recent murder victim dumped into a newly opened grave, and called Bass. His initial assessment—that the headless body had been dead no more than a few months—was widely reported in the local press.

In his laboratory beneath the south stands of the Volunteers' stadium, Bass carefully rendered the corpse down to bone, simmering off the flesh in restaurant-size pans filled with water laced with laundry enzymes. From the dimensions of the bones and other clues, he correctly determined the unidentified victim's race, height, and age. By contrast, Bass's estimated time of death, based on the extent of bodily decomposition, proved spectacularly inaccurate—off by 112 years. The victim turned out to be the man whose name was etched on the plot's gravestone: Lieutenant Colonel William Shy, killed at the Battle of Nashville by a musket ball to the head in 1864 and impressively embalmed with arsenic before being entombed in a cast-iron coffin. Apparently, vandals had busted open the coffin and pulled out Shy's largely intact body in a search for the colonel's valuable Civil War sword. Less well preserved, the fragments of Shy's shattered skull were retrieved from the far corner of the coffin.

A lesser scientist might have tried to hide such an exceptional blunder. But Bass has always stood out among his colleagues for his willingness, even insistence, on drawing attention to the limitations as well as the strengths of his science. His integrity has been, and continues to be, a spur to research into ways to better estimate time since death in the twilight zone.

NO OTHER SCIENTIST HAS ADDED MORE to the world's knowledge about time of death than Bass. But a reader looking for an in-depth accounting of time-of-death research won't find it in Death's Acre. The authors duly note the precedent-setting insect studies of Bass's protégé Bill Rodriguez, who forged a postmortem time clock from the growth rates of fly maggots feeding on a corpse. They likewise acknowledge the promising work of Arpad Vass, who has documented the step-by-step postmortem breakdown of the body's fatty acids. But nowhere is this work described in detail. Nor is the research behind some intriguing court testimony (in a triple homicide case) in which Bass alludes to his experiments retroactively calculating the rate of human decomposition by "accumulated degree days," a unit of time and temperature borrowed from forensic entomology. His findings, if reliable and reproducible, would be revolutionary. Unfortunately, the book doesn't describe these studies.

What comes through in this memoir is Bass's meticulousness, his generosity as a teacher and mentor, and his macabre but never disrespectful sense of humor. To explain the speed of insect-assisted decomposition in warm weather, for example, he repeats his aphorism that "Bugs, like people, prefer to picnic in the summertime." He also offers examples of how he determines an unidentified victim's age, stature, gender, and race by using telltale skeletal markers such as bone-length ratios and the degree of fusion between cranial plates.

One of the book's most intriguing anecdotes involves a set of overbaked bones found in the burned-out shell of a car after a "routine" traffic fatality. What the medical examiner missed and Bass found was a small, gray piece of skull deep in the layer of rubble in the floorboard under the driver's seat. The fragment's position and condition suggested that the body had been head-down on the floorboard during the crash and resulting fire, a strange position for a driver. Bass figured out that the victim could not have been the owner of the vehicle, a 34-year-old American financial advisor; it was instead more likely a 50- to 60-year-old Mexican laborer. Two years later, police arrested the not-so-deceased financial advisor, living near his family under an assumed name while waiting for the payout of his $7 million life insurance policy. (Not determined was whether the laborer was murdered or "borrowed" from a graveyard.)

IN 1994, THE POPULAR CRIME NOVELIST Patricia Cornwell captured the public's imagination with her fictionalized account of Bass's unique research facility, The Body Farm. Since then, the public's appetite for forensics has only increased, whetted by popular TV shows like Forensic Files, CSI, and CSI: Miami and a steady stream of true-crime books by forensic scientists, including pathologist Michael Baden's Dead Reckoning and anthropologist Mary Manhein's The Bone Lady.

Death's Acre is the latest in the string of bestsellers that have catapulted these once-obscure scientists to stardom. Understandably, many defense lawyers and other criminal attorneys have grown increasingly uncomfortable with the celebrity surrounding forensic scientists like Bass, who often leave juries star-struck when they take the stand.

While the Supreme Court rulings of Frye v. United States and Daubert v. Merrel Dow have raised the standards of scientific evidence that can be introduced to a jury, the celebritization of science may prove less manageable. Most troubling are the instances in which celebrity expert witnesses offer testimony beyond the limits of their disciplines. Bass, to my knowledge, has never committed such a sin. But Death's Acre does make the mistake of portraying Bass's determinations as simple and infallible. In the courtroom and among his peers, Bass is as known for his willingness to admit uncertainty as he is for his expertise. Death's Acre would have proved a better book if it had followed suit.

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