We are delighted to have been invited to be guest editors for this special issue on forensic document examination, a forensic science discipline that has had a long history of use in both criminal and civil investigations.

The work of the forensic document examiner (FDE) can encompass handwriting (including signature) comparisons, and examinations and evaluations of physical components of questioned documents such as paper, ink, toner, and impressions (of writing and stamps) to answer questions of authenticity or source.

A debate regarding the validity and reliability of forensic handwriting examination and other forensic comparison techniques that rely on human cognition and decision-making has been ongoing for several years. Furthermore, the risk of cognitive bias in forensic science generally and forensic handwriting examination specifically has been identified in the published literature.

Despite a declining reliance on handwritten signatures for business transactions, and increased use of digital technologies for both formal and informal communication, handwriting and signature comparisons and examinations of the components of physical documents still play an important role in forensic casework.

It has been only in relatively recent years that significant changes to the paradigm, particularly for handwriting examinations, have occurred, with a greater appreciation of the need to understand and define the scientific basis of the work. Technological developments have led to more objective approaches to handwriting examinations, and the ability to explore in greater detail the physical components of documents. Additionally, topics such as evidence interpretation, reporting and quality assurance are as relevant as ever for the FDE.

This special issue showcases research and commentary across a range of forensic document examinations and topics, demonstrating the continued relevance and shifting focus of the field.

Like any human-based method, handwriting examination is subject to bias and error due to various human factors. Crown et al. [1] present several tools and approaches to mitigate error in handwriting examinations, including contextual information management, checklists, blind peer review, logical reasoning (evaluative reporting) for the evaluation of findings, participation in regular testing, continuous improvement through training and education, and increasing objectivity by use of data and automated comparison systems.

Ostrum [2] provides a comprehensive but accessible discussion of questions that practitioners may have about evaluative reporting. Although the focus is on addressing questions for forensic handwriting examinations, much of the content is general in nature and may prove enlightening for practitioners in other disciplines.

With rise of digital documents and associated potential availability of dynamic data for examination, Okado et al. [3] provides a mathematical approach for analysis of global and local data from dynamic signatures, reducing subjectivity in handwriting examinations. Simulated, disguised and naturally written signatures were included in the study.

Two papers deal with the materials of documents. Yuan et al. [4] used desorption electrospray ionization mass spectrometry (DESI-MS) to analyse the ink composition of 227 gel pens, applying various data analyses to explore the extent to which different makes and models of these pens can be distinguished. Alvarez Cordeiro and Gondikas [5] investigated the visual and spectral characteristics of 15 different makes and models of thermochromic ink, using various visual/spectral techniques to characterize the inks in unaltered and heat-manipulated states. These two papers expand our knowledge on the characteristics of some writing inks and provide largely non-destructive methods for discriminating or identifying these, which may prove important in addressing questions of authenticity.

Finally, Tapps et al. [6] have highlighted their laboratory's experience in profiling features of counterfeit identity documents and cross-referencing with other records to link documents. This has enabled the laboratory to provide strategic intelligence and advice to relevant agencies that contributes to disrupting crime. The authors advocate for collaboration between forensic and criminal intelligence to proactively understand and tackle crime.

The contributions outlined above have been made by experts hailing from North America, South America, Europe, and Asia, providing a global snapshot. These articles focus on the frontier issues of handwriting and questioned document examination and contribute fruitful research to the discipline. Although legislation, business practices and technology relevant to forensic document examination, as well as examination approaches themselves, may vary from region to region, sharing information and advances can lead to increased knowledge and improved and harmonized practices. We hope that this special issue of Forensic Sciences Research, reflecting the work of FDEs around the globe, brings readers new information and ideas, and the FDE community closer together.

Both authors wrote and edited the manuscript and approved the final version.

This article does not contain any studies with human participants or animals performed by any of the authors.