The potential for application of ink stable isotope analysis in questioned document examination

Lesley A Chesson; Brett J Tipple; Janet E Barnette; Thure E Cerling; James R Ehleringer

doi:10.1016/j.scijus.2014.05.010

The potential for application of ink stable isotope analysis in questioned document examination

Sci Justice. 2015 Jan;55(1):27-33. doi: 10.1016/j.scijus.2014.05.010. Epub 2014 Jun 16.

Authors

Lesley A Chesson¹, Brett J Tipple², Janet E Barnette², Thure E Cerling³, James R Ehleringer²

Affiliations

¹ IsoForensics Inc., 421 Wakara Way, Suite 100, Salt Lake City, UT 84108, USA; Department of Biology, University of Utah, 257 S 1400 E, Salt Lake City, UT 84112, USA. Electronic address: Lesley@isoforensics.com.
² IsoForensics Inc., 421 Wakara Way, Suite 100, Salt Lake City, UT 84108, USA; Department of Biology, University of Utah, 257 S 1400 E, Salt Lake City, UT 84112, USA.
³ IsoForensics Inc., 421 Wakara Way, Suite 100, Salt Lake City, UT 84108, USA; Department of Biology, University of Utah, 257 S 1400 E, Salt Lake City, UT 84112, USA; Department of Geology & Geophysics, University of Utah, 115 S 1460 E, Salt Lake City, UT 84112, USA.

PMID: 25577004
DOI: 10.1016/j.scijus.2014.05.010

Abstract

We investigated a novel application of stable isotope abundance analysis of nitrogen (15N), carbon (13C), hydrogen (2H), and oxygen (18O) to characterize pen ink. We focused on both ballpoint and gel pen inks. We found that the isotope ratios of ink from pens purchased together in a package were similar and within-package stable isotope ratio variability was not significantly larger than the variability of isotope reference materials used during analysis. In contrast, the isotope ratios of ink from pens of the same brand purchased in three states of the continental USA were significantly different from each other and there was isotope ratio variation among pens of the same brand but different, unknown production periods. The stable isotope ratios of inked paper were statistically distinguishable using measured δ15N values. Paper inked with different gel pens was statistically distinguishable using measured δ2H values. The capacity of stable isotope ratios to differentiate among ballpoint inks as well as gel inks shows that stable isotope analysis may be a useful and quantifiable investigative technique for questioned document examination, although current sample size requirements limit its utility. Application of the technique in casework will require the development of micro-scale sampling and analysis methods.

Keywords: Carbon isotope ratios; Forensic science; Hydrogen isotope ratios; Isotope ratio mass spectrometry; Nitrogen isotope ratios; Oxygen isotope ratios.