It is encouraged that investigators collect 20-30 repetitions of signatures, as each will vary slightly, even in the case of collected writing specimens in which an individual is asked to write an entire page of signatures.
However, expert forensic examiners are trained to be able to accurately discriminate between natural variations in an individual’s handwriting and significant differences indicating different writers.
Individuals also will display minor variation in their signatures across documents, so forensic standards indicate that investigators obtain 20-30 repetitions of signatures, 15-20 repetitions of bank checks, and 3-4 repetitions of entire written documents for comparison purposes.
The last stage in the ACE-V methodology is verification, wherein a second expert document examiner retests the original hypothesis using the ACE process in order to determine whether it is possible to formally individualize or exclude particular information sets used for comparison.
Handwriting Examination and Comparison The examination of handwriting and signatures involves the comparison of writing on the document in question to additional samples in order to determine potential authorship.
Standards of Practice The American Society for Testing and Materials (ASTM) publishes standards for methods and procedures used by Forensic Document Examiners.
ASTM International is a global leader in the development and delivery of voluntary consensus standards, to improve product quality, enhance health and safety, strengthen market access and trade, and build consumer confidence.
The ABFDE requires that examiners obtain a minimum of a baccalaureate degree and complete a two-year, full-time training program or apprenticeship in a recognized forensic laboratory or with an established examiner in private practice.