Stable Isotope Forensics for identifying Residence Patterns
E Dotsika
*
Stable Isotopes Unit, N.C.S.R. “Demokritos”, Institute of Nanoscience and
Nanotechnology, 15310, Ag.Paraskevi Attikis, Greece
Abstract. In this study we investigate a method for determine the “residence patterns” of
human by comparing the oxygen isotopic composition of the meteoric water that an
individual was drinking, during his living period, with the oxygen isotopic composition of the
teeth enamel. Teeth samples were collected from two areas (Athens and Chalkidiki) of
Greece from individuals that never travelled and drank tap water. For these two regions the
isotopic method is a promising tool for discriminating the provenance.
1. Introduction
Methods for identifying remains include examination of the biological profile, fingerprint analysis,
dental records, artifacts from medical procedures, and DNA analysis. In cases where partial humans’
remains are found the above methods are inconclusive in identifying humans and investigators need
additional techniques for collecting characteristic information about the life history of the individual
before his death. The only method capable to provide information about the diet and residence
patterns of unidentified individuals (by examining bone, teeth, hair, and nails) is the isotope analysis.
The measurement of stable isotope abundances contained within materials, like human remains,
can provide information about the history and source of the materials. Stable isotope compositions
are used to discriminate between two materials by measuring the distinctive “isotopic signature” of
samples: two identical chemical molecules are isotopically different. As such, stable isotope
abundances play an increasingly important role in forensics analysis [1].
The use of stable isotopic analysis for predicting the life history of unidentified human remains
has generally proceeded on two fronts: evaluation of stable isotopes compositions in various natural
systems for understand biological and geological processes and subsequently generation of predictive
models. These models incorporate spatially variable isotopic parameters to construct isotope “iso-
land-scapes” and has been previously used for tracing the origin of unknown ecological (plants,
natural products, animals) and geological (soil, minerals and water) samples [1-4]. This isoscape
approach has provided an empirical framework from which is possible to predict the geographic
origin of unknown samples and so to identify the residence patterns of unidentified human remain
based on their isotopic signatures (bone, teeth, hair, and nails) [1, 5-7] (see Figure 1 for a schematic
presentation of the method).
228
Dotsika, E.
Stable Isotope Forensics for Identifying Residence Patterns.
In Proceedings of the International Workshop on Environmental Management, Science and Engineering (IWEMSE 2018), pages 228-231
ISBN: 978-989-758-344-5
Copyright © 2018 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved

Figure 1. Stable isotope ratio analysis in forensic investigations.
Also the scientific and technological progress in human epigenetics has begun to play an
increasingly important role in the establishment of “epigenetic fingerprint” from crime scene traces
to various forensically purposes and questions that cannot be answered through genetics [8-10].
These purposes include the prediction of forensically informative lifestyle and environmental
information of an unknown trace donor. Thus isotopic fingerprint, in conjunction with the biological
information from the skeleton, and the epigenetic fingerprint may aid in the investigation of missing
persons primary by limited the geographic region from which a person is originating (for example,
where he previously lived or travelled) and secondary predicting the lifestyle and environmental
exposures (socioeconomic status, activity, body size, alcohol and drug abuse, smoking, habits…) of
unidentified humans. In this framework we conducted stable isotope analysis of teeth samples of
known origin (Athens and Chalkidiki area) and compared them to the isoscape models of
18
O of
water from these areas. This method is a promising tool for predicting region of origin and residence
patterns of unidentified human remains.
2. Sampling and methods
The isotopic composition of carbonate and phosphate minerals in tooth enamel and bone bioapatite
reflects the isotopic composition of diet water (drinking water or water contained within food) [11].
There is a strong relationship between the oxygen isotope ratios of carbonate and phosphate minerals
and water consumed by an individual. Thus, for big mammals (like humans) the impact of food on
tooth and bone bioapatite oxygen isotope ratios is much less than the impact of drinking water.
By keeping in mind the existing relationship between oxygen isotope of water and oxygen ratio of
teeth and supposing no other identifying information or evidence available, we apply stable isotope
analyses to investigate potential geographic origins of the individuals in the years before death and
adolescence. In fact, teeth and bone can be considered “historic” recorders because teeth enamel is
formed when an individual is juvenile while the bone is continuously remodelled during the
individual’s lifetime [12]. Therefore, from the isotopic composition of diet water (measured in teeth)
of an individual it is possible to correlate with the isotopic composition of water of the region where
he lived before his death, and consequently to reconstruct his residence patterns. In this work we
analysed sprig water and enamel collected from molar, for both oxygen and carbon isotope ratios, of
known persons. In total, 15 teeth samples and 15 water samples were collected from the two areas.
Especially for the teeth samples, they are from individuals that they never travelled.
Any human tissue could be measured with Isotope Ratio Mass Spectrometer (IRMS). Abundances
of stable isotopes of an element are described as the ratio (R) of the rare or heavy form to the
common or light form (e.g., R =
18
O/
16
O or
2
H/H,
13
C/
12
C). The results are expressed in δ-notation as
parts per thousand (‰) difference from an accepted reference point, where:
δ = (Rsample/Rstandard − 1). This δ-notation is also used for expressing the stable isotope ratios of
hydrogen (H), carbon (C), nitrogen (N), and sulfur (S), collectively described as the bio-elements.
Stable Isotope Forensics for Identifying Residence Patterns
229

The error for δ
18
O, δ
13
C is ± 0.2 ‰ and for δ
2
H ± 1‰. Isotopic analyses were conducted at the Unit
of Stable Isotopes, Institute of Nanoscience and Nanotechnology, N.C.S.R. “Demokritos”.
3. Results
 The “residence patterns” approach of this study is based on the relationship of the oxygen
isotopic composition of the water that a known individual was drinking, during his living
period, with the respective oxygen isotopic composition of its teeth.
 To predict potential origins from the δ
18
O value determined for the tooth enamel, we first
converted carbonate measurements to equivalent phosphate data [13] and then predicted
drinking water [14] from the phosphate data. In order to achieve that, several equations from
international literature may be used, which practically convert the δ
18
O of the carbonate
component of the bioapatite (δ
18
O
C
) to δ
18
O of the phosphate component (δ
18
O
P
) and finally
to δ
18
O of water (δ
18
Ow). As so, the δ
18
O
C
(vPDB) values need to be converted into δ
18
O
C
(vSMOW) using the established equation:
 δ
18
OvSMOW=1.03091* δ
18
O vPDB+30.91 [15].
 According to Iacumin et al. (1996) the relationship between δ
18
O
P
and δ
18
O
C
values is
expressed by the equation δ
18
O
C
=1.015(±0.043)* δ
18
O
P
+8.79(±0.79), resulting through
studies on bone and tooth samples of modern mammals.
 For the conversion of δ
18
O
P
in δ
18
OwHoppe (2006) suggested an equation that combines the
structural oxygen with the consuming water: δ
18
O
P
=21.28(±0.51)+[0.68(±0.04)*δ
18
Ow].
The sampling for Athens (Figure 2), with δ
18
O of enamel between -6.5‰ and -6.3‰ suggest that
the individuals drunk water from the region of Athens (-6.5‰ to -5.0‰ with the majority being to -
6.5‰) where they passed all their lives (Athens Teeth 1). Teeth samples of individuals, which drunk
bottled water (Athens Teeth 2), indicate more negative isotopes values (-9.0‰ to -8.0‰). This is
expected because the measured stable isotope ratios of bottled water in Greece range from −9.2‰ to
−7.2‰ for δ
18
O
w
.
Teeth samples coming from Chalkidiki present more negative oxygen values (-8.1‰to -7.5‰) in
accordance with the isotopic values measured in spring water of the Chalkidiki (-9.5.0‰ to -6.5‰
with the majority being to -8.0‰).
Figure 2.
18
O from spring water and human teeth.
IWEMSE 2018 - International Workshop on Environmental Management, Science and Engineering
230

4. Conclusions
The “residence patterns” approach is based on the relationship of the oxygen isotopic composition of
the meteoric water and the oxygen isotopic composition of the teeth enamel. For the two regions
studied (Athens and Greece) this method (applied on known individuals that were drinking water and
never travelled outside of their residence) can discriminate the geographic origin of unidentified
humans. This method can potentially be applied for discriminating unknown human samples in a
wider region. An isoscape map of the drinking waters (tap water, springs and bottle waters) of the
region under investigation is required in order to compare and potentially narrow down or even
discriminate the origin of the unidentified human samples.
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