A Critical Evaluation of Current Ink Dating Techniques

Abstract

Advances in ways to date inks have been publicized over the past 17 years. As a result, Government agencies and the private sector now rely heavily on these techniques in criminal and civil litigations. As new procedures have become known, more forensic scientists are asked to perform ink dating examinations. While the capabilities of these techniques are generally known, their limitations are not. This paper evaluates the current approaches used for dating writing inks and takes a critical look at conclusions that can be made on the basis of the different laboratory techniques.

Photofading of ballpoint dyes studied on paper by LDI and MALDI MS

“…This observation can be explained by solvent evaporation that takes place after the application of the ink on paper. Resins and dyes are then expected to form a more compact surface [1].…”

“…After deposition on paper, the ink composition begins to change qualitatively and quantitatively: the resins polymerize, the solvents evaporate, and the dyes fade. Throughout the years, many different methods were developed to measure the changes occurring in the ink with time [1][2][3][4][5][6][7]: decrease of extractability of ink through hardening of the resins [8 -13, 16], disappearance of solvents [14 -20], and degradation of dyes [18,[21][22][23][24][25][26][27][28][29]. The analysis of the latter compounds involve techniques such as microspectrophotometry [21], HPLC analysis [25,26], or recently mass spectrometry [18, 22-24, 27, 28].…”

A GC/MS study of the drying of ballpoint pen ink on paper

“…For this reason the accurate dating of ink entries has always been of high interest for the document examiner and a large number of methods have been developed throughout the years [1][2][3][4][5][6][7] focusing on the aging processes of the substances contained in the ink such as resins, dyes and solvents. Since the aging processes are strongly influenced by the environmental conditions to which the ink entries are exposed (temperature, humidity, light), these methods cannot deliver unambiguous answers except for a relative dating of ink entries (comparison of entries of the same ink formula, on the same paper and aged under the same conditions).…”

Minimum requirements for application of ink dating methods based on solvent analysis in casework

“…It was based on the changes in the extractability of the ink supposedly caused by the hardening of the resins [10,[21][22][23][24]. The use of this technique in caseworks was reported in the literature [18,25], but it was followed by a vigorous controversy among the scientific community about the limitations of this approach [5,[26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. Several researchers tried reproducing the results obtained in previous studies and reported the methods to be unreliable [28,[34][35][36], while other scientists debated about the necessity for inter-laboratory validation before their use in casework [4,27,[31][32][33]38,41].…”