Detecting Forged Signatures

Detecting Forged Signatures


Examining a suspect signature on a document is a frequent request received by a forensic document examiner. Deciding if the signature is genuine or not requires careful examination of several facets of the signature including line quality, speed, letter formations, height relationships, and size.  Because signatures are the most common type of forgery, suspect signature cases appear in the authentication of sports memorabilia, contested wills and deeds, employment contracts, and checks.   Sometimes a signature can be identified to a known writer through a handwriting comparison, however many signature examinations cannot be definitely determined due to limiting factors. If limiting factors interfere with the examination, the conclusion falls within a range of probability.   The ability of a document examiner to detect a forged signature is challenging in today’s digital age. This article focuses on methods of forged signatures and detection techniques.


Several methods are used by forgers to place a spurious signature on a document.  A “simple” forgery is when the forger does not know what the genuine signature looks like  and writes the signature in their own handwriting style.  This type of forgery is the easiest to detect because the forger makes no effort to simulate the signature they are trying to produce.  Because the signature is generally written in the forger’s own handwriting, it   could be identified through a handwriting comparison.


A second method involves simulated signatures.  Simulations may be rapidly prepared with little effort by the forger to study the signature or practiced over many days.  A “practiced” simulation means the forger has access and time to perfect the signature he/she wishes to simulate. Generally, a forger using this method will prepare the signature with speed but the letter formations will suffer or vice versa,  the letter formations will be correct but the speed of the signature appears slowly prepared.  It is difficult for a forger to completely discard their natural writing habits and acquire the writing habits of the person who’s signature they wish to simulate.  A practiced simulation is more difficult to detect because pictorially it looks similar to the victim’s signature and will show a considerable degree of similarity to the more obvious features of letter design.   However, subtle differences that the writer is not conscious of performing like pen pressure, speed, height relationships, and connecting strokes can be discerned with a microscope.


Detecting a forged signature begins with an original document and a wet ink signature. Forms of forged signatures include tracings, manipulations, and deception.  With a tracing, the writer may not be confidant that they possess the skill to successfully simulate the signature on their own so they depend on a model signature for guidance.  Side lighting the document may uncover indented impressions around the signature area which may indicate a tracing was attempted.  Manipulated signatures can come from a genuine source(s) but  are cut and pasted onto a fraudulent document using desktop publishing, a photocopier, or some combination of current technologies. Careful study of the placement of the signature on the document, alignment, fonts, and spacing are just a few of the areas of concern. Sometimes a signature is genuine but is obtained under false pretenses and deceitful means.  The elderly are often targets for this type of forgery when different documents are substituted without their knowledge or consent.

Other types of forgeries include “guided hand”  and autoforgeries.  Guided hand forgeries are frequently encountered with an ageing writer who depends on their caregiver to guide their hand/arm while signing checks, etc. The signature may not appear natural as two individuals are guiding the signature across the page.  Sometimes, the aging writer may cease signing their names and the caregiver continues to sign important documents.  These types of cases are extremely difficult and considerable care must be taken in the analysis. Lastly, autoforgeries is a class of forgeries when a person simulates their own signature, changing a few characteristics, to later claim the signature is not theirs due to some minor defect.  These types of forgeries are considered remote but have been known to occur where large sums of money were at stake.


Detecting a forged signature is difficult but with proper training, tools, time, and following standard procedures, a document examiner should be able to determine whether a questioned signature is genuine or not.