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Postmortem Bone Dating | Stomach Contents | Tree Rings


Plant anatomical features have long been used by archeologists and paleontologists to characterize archeological sites, and since the 1930s have become increasingly more common in forensic applications (Lane et al., 1990). The cell wall is particularly important for two reasons: it is not easily digested by most organisms and therefore persists when other plant features are destroyed (Bock and Norris, 1997), and the size, shape, and pattern of cell walls is often taxon-specific (Lane et al., 1990). In addition to cell walls, many plants posess unique cell types, such as the sclereids of pears or species-specific trichomes, which are useful in identifying botanical material (Lane et al., 1990).

POSTMORTEM BONE DATING

 

It can be a challenge to estimate the time since death for a body when only bones remain. Plant roots, like their above-ground counterparts, exhibit annual growth rings that can be useful in pinning down the post-mortem interval, or at least the time since the body came to be at the location where it was found (Willey and Heilman, 1987).

Roots are frequently found with exposed or shallowly buried bodies (Willey and Heilman, 1987). Quatrehomme et al. (2000) outline three ways in which the roots can be used to date the remains or otherwise characterize the burial site:


(1) Examine root development after it has been damaged. When a grave is dug or the ground otherwise disturbed, roots can be damaged but still continue growing. If the meristematic zone is damaged, no secondary xylem cells can be produced, leaving a permanent lesion. The number of growth rings laid down after the lesion indicates the number of years since the damage occurred.


buttercup root slide, 16.5kb

Cross section of buttercup root, Ranunculus sp. Source: BIODIDAC.


(2) Examine roots in direct contact with the remains. Roots in contact with the bones or personal effects of the deceased can be cross-sectioned at the point of contact and the annual rings counted, establishing a minimimum time frame for time since death. The contact must be penetrative, i.e. the roots must be growing through clothing or bones, in order for the interpretation to be valid (Willey and Heilman, 1987).

(3) Examine branch growth. Annual longitudinal growth of the roots, in addition to radial growth, can be estimated, and a time frame determined from the length of a root from its point of contact with the remains to its distal end.

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STOMACH CONTENTS

 

Characteristic cell types from food plants can be used to identify a victim's last meal; knowledge about which can be useful in determining the victim's whereabouts or actions prior to death (Bock and Norris, 1997). Some of these cell types include (Dickison, 2000):

  • sclereids (pears)
  • starch grains (potatoes and other tubers)
  • raphide crystals (pineapple)
  • druse crystals (citrus, beets, spinach)
  • silica bodies (cereal grasses and bamboos)

In a case where a young woman had been stabbed to death, witnesses reported that she had eaten her last meal at a particular fast food restaurant. However, her stomach contents did not match the limited menu of the restaurant, leading investigators to conclude that she had eaten at some point after being seen in the restaurant. The investigation led to the apprehension of a man whom the victim knew, and with whom she had shared her actual final meal (Dickison, 2000).

Time since death can be approximated by the state of digestion of the stomach contents. It normally takes at least a couple of hours for food to pass from the stomach to the small intestine; a meal still largely in the stomach implies death shortly after eating, while an empty or nearly-empty stomach suggests a longer time period between eating and death (Batten, 1995). However, there are numerous mitigating factors to take into account: the extent to which the food had been chewed, the amount of fat and protein present, physical activity undertaken by the victim prior to death, mood of the victim, physiological variation from person to person. All these factors affect the rate at which food passes through the digestive tract. Pathologists are generally hesitant to base a precise time of death on the evidence of stomach contents alone.

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TREE RINGS

 

Dendrochronology is the study of tree rings. These annual growth rings occur because the xylem cells get gradually smaller in radius as the growth season proceeds into the dormant season. There is an abrupt change in size from small, late season cells to the large, early season cells of the following spring (Willey and Heilman, 1987). The number of rings gives the tree's age, and the variation in ring width reflects environmental conditions (Schweingruber, 1988). Ring patterns of several samples from a given geographic area subject to similar environmental conditions are cross-dated, giving standardized chronologies (curves) for different species in different areas, to which specimens of unknown origin can be compared (Schweingruber, 1988).

Dendrochronology is an important technique in a number of disciplines, including archeology, paleontology, paleobotany, geomorphology, climatology, and ecology. Forensic applications concern the dating of wooden objects and matching objects with crime scenes using the wood's morphological features.

Art Fraud

Tree ring analysis is a common technique for dating masterworks by European painters, many of which were painted directly on wood. Given that the samples are in good condition, analysts can pinpoint the exact year when the tree, from which the wood for the painting was taken, was cut down. A Peter Paul Reubens painting orginally dated 1616 was shown to be at least 10 years younger, and a painted wall panel recovered from a house in Switzerland in the 1970s was determined to have been painted on spruce harvested in 1497 (Schweingruber, 1988).

 

Dendrochronology techniques are useful in determining the provenance of wooden art objects and musical instruments. In one case, two violins forming part of an inheritance were purported to have been made by Antonio Stradivari. The sounding-boards of the instruments were x-rayed and compared to standard curves for spruce from the Alpine region of northern Italy, where Stradivarius is known to have worked. The oldest rings from the samples dated to 1902 and 1894 respectively for the two violins. Furthermore, these oldest rings were not the outermost rings of the wood from which the violins were constructed. Allowing for a period of seasoning before the wood could be used to make the instruments, analyses showed that the violins could not have been made before 1910. Given that Stradivari did his best work at the turn of the 17th century, the instruments were deemed to be fakes (Schweingruber, 1988).


violin

Spruce violin circa 1850. Photo courtesy of John Topham.


Rail 16: The Kidnapping of Charles Lindbergh, Jr.
(S. Graham, 1997)

Sometime during the evening of March 1st, 1932, the infant son of famous American aviator Charles Lindbergh was kidnapped from the second-floor nursery of his home in Hopewell, New Jersey, US. The family paid a $50 000 ransom, but their son was never returned. His body was discovered two months later a few miles from the family home.

A critical piece of evidence in the case was a crude homemade wooden ladder left at the scene. Xylotomist Arthur Koehler of the United States Forest Service undertook a meticulous examination of the ladder and when the case finally came to trial four years later, offered the first botanical testimony ever to be heard and accepted in American courts.

The ladder had been constructed in three sections, presumably for ease of transport. Koehler identified each side rail and rung with a number and identified each piece to species. Through careful examination of the characteristic milling marks left on each piece and comparisons with local mills, he was able to trace all components of the ladder back to their respective retail sources. He also noted distinctive marks left on the wood by a dull, nicked hand plane. Of particular interest was rail #16, a piece of low-grade pine which had four distinctive square nail holes. It was also relatively unweathered. The low grade of the wood, the nail holes, and its unweathered condition suggested that particular piece of wood had been removed from some interior construction, like a barn or shed.

Without a suspect however, progress on the case was slow. In September of 1934, some of the notes used to pay the ransom were used at a gas station by Bruno Hauptmann, a carpenter who lived in the Bronx, New York City. He was arrested when $14 600 of the ransom money was found in his garage.

Upon searching the attic for more ransom money, police noticed that one of the floorboards was eight feet shorter than the others. The square nail holes in rail 16 lined up exactly with holes in one of the attic floor joists, and the annual ring pattern of rail 16 matched that of the short floorboard. A hand plane recovered from Hauptmann's garage was indeed dull and damaged, and made marks identical to those on the ladder and on a homemade shelf in the Hauptmann garage.

Hauptmann was convicted of kidnapping and murder and was executed on April 3rd, 1936.

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The Forensic Botany site was created in 2002 by Jennifer Van Dommelen as a project in the Web Literacy For the Natural Sciences class at Dalhousie University, Halifax, Canada. Terms in bold are defined within the body of the text. Highlighted terms and author citations are linked to a glossary and reference list, respectively, which open in new windows. All images have been used with permission. Header banners created by Jennifer Van Dommelen.

Last content update: April 2002
Last editorial/layout update: 17 June 2005

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