Introduction to the Handwriting and Signature Examination Method
Forensic Handwriting Experts (FHE’s) are called upon to provide their expert opinions regarding a wide range of issues associated with the comparison of handwriting (either text based or signatures). FHE’s express opinions regarding the authorship of writings and also the process of production (for example whether a signature is the product of ‘simulation’ (copying) process). FHE’s draw their skill and expertise from a wide variety of sources. These include training programs within laboratories or specialist society meetings, the scientific literature relating to the discipline and a number of dedicated texts (see for example Osborn, 1929; Harrison, 1958; Conway, 1959; Hilton, 1982; Ellen, 1989; Huber & Headrick, 1999, and scientific journals associated with forensic document examination.
Handwriting is a complex learnt motor behavior that is carried out, at least to some extent, by most members of the population. Individuals are generally taught a copy-book system of writing (one through formal education is considered the to be the model for the handwriting they are to produce). There are many copy-book systems taught throughout the world. Huber & Headrick, 1999, list 76 different systems in North America alone. What makes skilled handwriting a useful form of evidence in the forensic environment is that it is found to be a relatively stable behavior within the writer but it does vary markedly between different writers, even when people are taught exactly the same copy-book system.
As with most forms of forensic identification evidence it is this ‘inter-individual’ variation that provides us with a useful tool to determine whether there is a nexus between a particular writing act and a person (or another writing act). Handwriting as a learnt behavior is however subject to a number of variables that can make the examination process quite complex. Examples of these variables are the intra-writer variation (the variation in the handwriting within an individual which is observable as slightly different handwriting each time a sample is produced) and the reality that people can change their handwriting purposefully (disguise) or copy the handwriting of others (simulation).
There are a large number of variables that can impact on an individual’s ability to produce handwriting in a consistent fashion in relation the model they were taught. These include the complexity of the original copy-book system, the writers propensity to consciously modify the characters or connections away from the copy-book system, subconscious modifications to the movements (which may occur in order for them to improve the efficiency of their movements), the writers motor skill level and capacity, and the biomechanical / postural restrictions associated with any given writing event. Complicating the system is that individuals can purposefully change their motor output, and therefore the handwriting that they produce, and can therefore attempt to disguise their own handwriting characteristics or imitate (simulate) the images produced by others to some extent.
In the very simplest of forms the process of handwriting comparison and identification can be described as follows. Examiners are provided with a handwriting sample (whether text based or signatures) whose author is considered unknown or disputed. This sample is termed ‘questioned’. The questioned writing is compared to another sample of writing (a ‘comparison sample’). This comparison sample could be writing submitted as having been written by a particular person (a ‘specimen’ or ‘exemplar’) or it could be another sample of questioned writing (termed a ‘common authorship’ examination). Specimen writings are the most frequently encountered form of a comparison sample. These may be either ‘requested’, where the content of the handwriting is dictated to the individual, or ‘collected’ where the investigator, or client, locates samples of an individuals day to day writing. The comparison sample is examined and pictorial and structural features that the examiner believes characterize the handwriting are assessed. These features are compared to the features associated with the questioned sample. If it is found that the questioned features are similar to the specimen features then propositions are advanced which could account for the similarities. Should the examiner be of the opinion that there is evidence to support the proposition that the that the similarities result from both the questioned and specimen images having been produced by the one writer then the handwriting is said, with some level of confidence. to be ‘identified’. Alternatively if the features are found to be dissimilar to the questioned images , explanations are proposed that could account for the dissimilarities, and in some instances the examiner will be of the opinion that there is evidence to support the proposition that handwriting was not written by the specimen writer.
It must be remembered that handwriting is a behavioral artifact. As a behavior, handwriting evidence is subject to a number of potentially limiting factors which include:
- No amount of handwriting will fully characterize the extent of the variation in the behavior or describe exactly the characteristics of the system which controls its generation.
- It is still not possible to determine objectively the relative frequency of any particular handwriting feature in the population.
- The fluency of the movement can change over the course of different writing events.
- The features of the writing may change naturally over time.
Added to these considerations is the reality that the instrument performing the examination and comparison of handwriting in the forensic environment is the FHE’s brain. The technique is therefore based on human perception and cognition and is subject to normal variation with respect to these processes. Handwriting examination therefore should be referred to as ‘opinion identification evidence’ whereby expert opinion refers to the examiners belief in the extent to which the evidence supports that the writer of the comparison sample did or did not write the questioned writing.
Handwriting examination involves more than solely the ‘identification’ or ‘exclusion’ of writers as having written a particular sample of questioned writing. The discipline also deals with the elucidation of handwriting processes. Handwriting processes are behaviors that can be inferred from information within the images. Examples of processes investigated may be disguise, simulation behavior (whether performed unassisted or as a tracing), and machine-generated handwriting.