The assessment of the impact of induction spatial effects on magnetic flux measurements of toner-printed documents to the detection of forged or altered documents.

Magnetic flux measurements of toners can aid in the rapid differentiation of toner-printed specimens in the context of investigations of forgeries or alterations of printed documents. However, some variables that may impact magnetic flux measurements, including hysteresis effects, are not currently well understood. This study assessed the impact of hysteresis and other induction spatial effects on magnetic flux measurements of toners analyzing five toner-printed samples produced from different devices. The samples were printed with controlled grids of square, rectangular, and elongated rectangular blocks with the same area. Thirty measurements were conducted on each sample, on each grid type. The measurements were repeated in planes of rotation 90°, 180°, and 270° counter to this original position. The values obtained for the square grids were evaluated using one-way ANOVA to assess the presence and impact of hysteresis effects. The values obtained for the rectangular grids were compared with those obtained for the square grids using a two-way ANOVA to determine potential induction current orientation effects. The results of both one-way and two-way ANOVA were significant with p < 0.05, indicating that both hysteresis effects and induction current spatial effects contribute significantly to variations in magnetic flux measurements. Results confirmed that sensor orientation is an important factor that must be accounted for in method protocols for the measurement of magnetic flux of toners. Controlling these variables is a step forward toward the development of a reliable screening method to be deployed in the context of investigations of document forgeries or alterations.

Technical note: A preliminary evaluation of a method for the examination of text substitutions using magneto-optical measurements.

Recent developments regarding the detection and measurement of the magnetic heterogeneity between texts produced with two different laser printers were evaluated. The present exploratory study focused on letter- and word-size fragments of texts inserted in a document to simulate the context of printed document alteration by addition. The measured values from genuine samples were used to create model arrays with the replacement or insertion of a letter or a word into the text of a base document. These model arrays were analyzed using newly introduced software features (named "induction at the point", "target", and "fragment" functions) enabling the targeted selection and isolation of small subsections of the total sensor area of the magneto-optical measuring device used in this study. It was observed that magnetic measurements of letter- or word-size fragments using the proposed methodology to the tested models allowed detection of text alterations by insertion that could not typically be detected with magnetic measurements over the full field of view of the magneto-optical device.