Determining line-crossing sequences between laser printing and black ink using digital microscopy: the influence of writing tool and toner.

One of the recurring issues in forensic document analysis is determining the chronological order of line-crossing sequences. This seemingly simple but tricky task allows forensic laboratories to demonstrate the real order of events. The aim of this work is to analyse black ink/toner intersections using the digital microscope Hirox RH-2000. Five types of pens (ballpoint, gel, rollerball, fountain and fineliner) as well as five different laser printers were used to create the samples. Forensic examiners were tasked with assessing toner fractures, the bronzing effect, and gaps. The findings were analysed to determine the importance of each characteristic for each type of pen. Results indicate that observing the bronzing effect at high magnification (700x) is crucial for establishing the sequence order of application. In this regard, the fineliner pen is considered the most challenging type of pen to analyse in a black ink/toner intersection. The method was validated through a blind test. Based on this, a flow chart has been developed to assist the Forensic Document Examiners (FDEs) in their evaluations. The flow chart emphasises the significance of combining multiple observations and enables a more objective analysis for trained FDEs.