Video Presentation

Determining the integrity of two ink strokes in a crossing is an ongoing investigative challenge. While the field has had many technological advancements, current methods of ink dating are highly subjective, primarily dependent upon the experience level of the investigator. The field also lacks a true understanding of how two inks distribute within a crossing. This information, however, may be key evidence for the completion of a civil or criminal investigation. Therefore, this study was completed to objectively observe the actual distribution between inks within the interior of their crossing. Sixteen crossings made from unique combinations of four blue gel pens (Bic Cristal, Uniball Signo, Bic Pro, and Pilot G2) were prepared on white office paper. The perpendicular crossings were cut using a scalpel to expose the depth of the two ink layers. The University of Pittsburgh's Raman Spectrometer equipped with a microscope was used to analyze each sample with a 20X objective and a 473 nm laser. From the sixteen unique ink combinations, multiple drying times between ink layers (horizontal ink and vertical ink) were also analyzed (0, 12, 36, or 48 hours). Experimental conditions were optimized before sample analysis. The Raman microscope mapped the chemical signatures present within each crossing, with a constant approximate value of 300 data points measured. Preliminary data analysis using Multivariate Curve Resolution (MCR) method revealed chemical images which show the actual distribution of each ink within the crossing. The intention is to create a model with this information that will help investigators objectively identify the legality of the ink crossing in question.