Time-series averaging and local stability-weighted dynamic time warping for online signature verification

Discrimination and source correspondence of black gel inks using Raman spectroscopy and chemometric analysis with UMAP and PLS-DA

Document dating is an important and challenging task in the field of forensic science. With the development of analytical techniques, related methods are emerging for document dating studies. Desorption electrospray ionization–mass spectrometry (DESI‐MS) is an ambient ionization‐MS technique that has been applied in the forensic discrimination of inks. This study focused on utilizing DESI‐MS to distinguish between ink entries of different ages. Blue ballpoint ink and black gel ink samples were artificially aged by heat and light exposure and then screened by DESI‐MS in the positive ion mode, with a methanol–water‐formic acid solution (90:10:0.1%, v/v/v) as the desorption solvent. As a result, the artificially aged ink samples were directly differentiated from the reference ones in the chemical images of age‐dependent compounds such as basic dyes or polyethylene glycol derivatives. The amount of ethoxylated fatty amine surfactants in copy paper was also found to decrease after artificial aging. Moreover, this method enabled us to visualize the differences between the composition of naturally aged and fresh ink samples. It has been proven to cause no apparent destruction of the samples. The identification of chronological changes in document materials suggests that the DESI‐MS method is a promising approach for relative document dating.

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

Online signature verification is the process of using a dynamic signature verification system to confirm the writer’s identity. It can be used as a security system to confirm entrance applications and password substitutes, as well as a forensic tool to assist an expert’s investigation. This study proposes a novel online signature verification system based on a single-template strategy to improve performance in real-world scenarios. It employs discriminative mean signature template sets as well as fusion strategies of multiple local weighting and warping schemes, for dynamic time warping (DTW). The first step is to generate a set of user-specific mean signature templates for each feature using a recent time-series averaging method, namely, Euclidean barycenter-based DTW barycenter averaging. Then, using multiple and direct matching points between the mean signature templates and references for dependent and independent DTW, we obtain a local weighting estimate considering local stability sequences. Furthermore, we develop fusion strategies for calculating locally weighted DTW sets and concatenating them as a feature vector for each warping, followed by the construction of a support vector machine (SVM) classifier. Finally, in the verification phase, we use the single-template technique to compute a discriminative fused score using SVMs between the mean signature template sets and a query sample. The effectiveness of the proposed method is demonstrated by extensive experimental results obtained using three public online signature datasets: SVC2004 Task1/Task2 and MCYT-100. 

Online Signature Verification Using Locally Weighted Dynamic Time Warping via Multiple Fusion Strategies

Pen ink discrimination in handwritten documents using statistical and motif texture analysis : A classification based approach

This review paper covers the forensic-relevant literature in questioned documents from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol Review Papers 2019.pdf .

Capitaine Marie Deviterne-Lapeyre

Papers

Interpol review of questioned documents 2016-2019.