# Calculation and Interpretation of Inter-laboratory Variation in Isotope Delta (δ) Values Using Real Interpretative Differences

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Published: Oct 20, 2021
DOI: https://doi.org/10.5744/fa.2020.0050
Keywords:
forensic anthropology, forensic science, stable isotope ratio analysis, accuracy, reliability, quality assurance

## Main Article Content

Lesley A. Chesson
Defense POW/MIA Accounting Agency
Thuan H. Chau
SNA International
Amelia J. Edwards
SNA International
Gregory E. Berg
Defense POW/MIA Accounting Agency

## Abstract

Building on applications in anthropology, the use of stable isotope ratio analysis of human bone collagen to investigate an individual’s life history is becoming more commonplace in the forensic science community. Careful consideration of the resultant isotope delta (δ) values, particularly in regard to their accuracy and reliability, is paramount when introducing isotope data into the U.S. court system. In this study, we use a simple framework to calculate real interpretative difference (RID) values for collagen (“col”) and assess isotope data comparability for sample analysis (RIDanalysis) as well as sample preparation/analysis combined (RIDcombined). The RIDcombined values of 0.59‰ for δ13Ccol and 0.91‰ for δ15Ncol are similar to more complex, published calculations of inter-laboratory variability in the stable isotope analysis of skeletal remains, but they are easier to calculate and intuitively elegant. The RIDcombined as well as RIDanalysis values presented here allow users to examine multiple sources of inter-laboratory isotopic variation (preparation, analysis, and both together) in a two-step process whereby a RID value is constructed and then tested. Implementation of this RID approach will provide surety for the legal and research communities in forensic applications of stable isotope ratio analysis.

## Article Details

Issue
Vol. 4 No. 3 (2021)
Section
Research Articles