The forensic analysis of office paper using oxygen Isotope Ratio Mass Spectrometry, part 2: Characterising the source materials and the effect of production and usage on the δ18O values of cellulose and paper

- Oxygen isotopic abundance values were measured to examine the paper production process.
- Effects of common printing processes and forensic examination techniques also examined.
- Some changes in isotopic values were observed between clean and used papers.
- Results will be used to inform sampling protocols and interpretation of oxygen values.

For casework applications, understanding the source processes used to create a material and the effects of those sources on the results obtained by Isotope Ratio Mass Spectrometry (IRMS) of a bulk material is important. Likewise, understanding the effect of environment, home/office printing processes and some forensic testing in at least a basic context, ensures that in casework, enough information on the effects of these variables is available during comparison and interpretation.In this study, which focuses on oxygen isotopic abundance measurements, both fractionation and mixing effects were observed within the pulping and production process. Also observed in the carbon isotopic experiments, sampling that included toner changed the measured isotopic abundance values of the paper and should be avoided in casework. Inkjet printing processes were not shown to have an effect on the paper oxygen abundance values. Samples that were treated for fingerprints using 1,2-Indandione-Zn prior to sampling showed the greatest risk for misinterpretation of whether two samples had originated from the same source. While this study provides a good basis and understanding of the effects of a range of factors on document paper oxygen isotope values, further testing for a range of specific casework scenarios is required and should be undertaken on a case by case basis as the need arises.