292 Forensic dentistrycold temperatures, or within a few hundred years of the burial, the age of
an individual at death could be deduced using the extent of aspartic acid in
tooth enamel from skeletons in cemetery populations.”
Mörnstad et al. showed that high-performance liquid chromatography
(HPLC) can be used instead of amino acid analyzers, making determinations
faster and less expensive.^168
Reported accuracy of this technique for estimation of chronological age
in adults varies. Carolan and coworkers concluded that age estimation based
on racemization is similar in reliability to other dental methods.^162 Waite et
al., by contrast, indicated that with proper sampling and analytic techniques,
this method provides a simple, cost-effective solution to age estimation in
adults, and can achieve accuracy within the range of ±3 years.^169 Seitz et al.
have reported success in detecting ratios using whole teeth and HPLC cou-
pled with mass spectroscopy.^170
13.4.7 Enamel Uptake of Radioactive Carbon-14Spalding et al. reported in 2005 the development of a new method of age esti-
mation from dental enamel.^171 Aboveg rou nd nuclea r test i ng f rom 1955 to 1963
produced greatly increased atmospheric levels of the radioactive carbon-14
isotope (^14 C). The increased^14 C isotope levels rapidly generalized around the
globe. The atmospheric levels of this isotope had been stable at much lower
levels prior to 1955. Since the cessation of testing in 1963 the levels have been
decreasing exponentially. The half-life of^14 C is 5,730 years. Atmospheric^14 C
reacts with oxygen to produce CO^2 with the radioactive signature. That radio-
active CO^2 is taken up by plants worldwide. Eating those plants and animals
that eat those plants causes^14 C uptake in the metabolically stable tooth enamel
as it is formed. By calculating the levels of^14 C with consideration of known
tooth development data for the specific tooth tested, an estimated date of birth
c a n b e c a lc u l at e d. I n it i a l t e s t s on t we nt y-t wo i nd i v idu a l s of k now n a ge re s u lt e d
in estimates that were reported to be accurate within about 1.5 years. The
technique is useful only for individuals born after 1943 since the formation
of the enamel of the third molars is completed at approximately age twelve.
Third molar enamel^14 C levels of 0 would indicate only that the individual was
born before 1944, but even this could be useful forensic information. Teeth
samples were collected and prepared at Karolinska Institute, Stockholm,
Sweden, and^14 C levels were determined by accelerator mass spectrometry at
Lawrence Livermore National Laboratory, Livermore, California.^171 In 2009
Druid et al.^172 proposed combining aspartic acid racemization analysis and
(^14) C studies to provide investigators of unidentified body cases with more use-
ful information. The age at death estimate from aspartic acid racemization
analysis combined with the date of birth from^14 C levels could, by calculation,
provide investigators with the estimated date of death.