Ink dating part II: Interpretation of results in a legal perspective

Abstract

The development of an ink dating method requires an important investment of resources in order to step from the monitoring of ink ageing on paper to the determination of the actual age of a questioned ink entry. This article aimed at developing and evaluating the potential of three interpretation models to date ink entries in a legal perspective: (1) the threshold model comparing analytical results to tabulated values in order to determine the maximal possible age of an ink entry, (2) the trend tests that focusing on the "ageing status" of an ink entry, and (3) the likelihood ratio calculation comparing the probabilities to observe the results under at least two alternative hypotheses. This is the first report showing ink dating interpretation results on a ballpoint be ink reference population. In the first part of this paper three ageing parameters were selected as promising from the population of 25 ink entries aged during 4 to 304days: the quantity of phenoxyethanol (PE), the difference between the PE quantities contained in a naturally aged sample and an artificially aged sample (R) and the solvent loss ratio (R%). In the current part, each model was tested using the three selected ageing parameters. Results showed that threshold definition remains a simple model easily applicable in practice, but that the risk of false positive cannot be completely avoided without reducing significantly the feasibility of the ink dating approaches. The trend tests from the literature showed unreliable results and an alternative had to be developed yielding encouraging results. The likelihood ratio calculation introduced a degree of certainty to the ink dating conclusion in comparison to the threshold approach. The proposed model remains quite simple to apply in practice, but should be further developed in order to yield reliable results in practice.

Emerging Approaches in the Analysis of Inks on Questioned Documents

“…Paper analysis was not considered in this chapter, neither were ink dating and ink line sequencing [17,21,22] asit is well known that the potential of optical methods remains very limited for the purpose of ink dating and sequencing. To date, the most promising technique relies on solvents analysis for ink dating purposes using gas chromatography (GC) or liquid chromatography (LC) coupled to mass spectrometry (MS) [23,24]. For Weyermann Céline, Techabowornkiat Korn-usa, 2019/10/01.…”

Application of chemometric methods for the determination of fading and age determination of blue ballpoint inks

“…[6] The study of the ink, namely, its differentiation and dating, is one of the most appealing challenges of forensic studies. About 28 methods of dating ink [2,[6][7][8][9][10][11][12][13] have been proposed since 1984. Several factors are involved in ink ageing, and the proposed models have only taken into account some of them [13] ; moreover, the models have several limitations and work properly for only few types of inks.…”

“…About 28 methods of dating ink [2,[6][7][8][9][10][11][12][13] have been proposed since 1984. Several factors are involved in ink ageing, and the proposed models have only taken into account some of them [13] ; moreover, the models have several limitations and work properly for only few types of inks. The advances in the ink dating field and development of analytical methods observed in the last decades were reported by Ezcurra et al [11] In the case of ballpoint pen inks, methods for determining the approximate or relative age of an ink are commonly divided into three groups.…”

Comparative analysis of aged documents by desorption electrospray ionization–Mass spectrometry (DESI‐MS) imaging

“…delicate procedures are required to compare the relative amounts of target compounds in ink dating [9,10].…”