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Module 10 Line quality and skill


Module 10 Line quality and skill

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									                                    Module 10

                           Line quality and skill

At this stage of the method it has been determined that the fundamental dissimilarities
are associated with the line quality and that the questioned writings are likely to be
simulated. This module overviews the rationale for determining whether the line
quality associated with the questioned material is indicative of a more or less skilful
writer. This determination, if it can be made at all, will focus the examination either
on the processes associated with simulation behavior, or may provide support for the
proposition that the writer of the comparison sample did not write the questioned

A fundamental component of handwriting comparisons is the examination of the line
trace in terms of its 'quality'. Line quality in the forensic environment refers to the
relative fluency or dysfluency observed in the written line trace. Examiners infer
characteristics associated with the dynamics of pen movement and therefore also the
motor control system from the qualitative assessment of line quality. Thomassen and
van Galen (1997) provide an overview of the dynamic order associated with skilled
handwriting and discuss possible approaches to reintroduce dynamic components into
static line traces. Found, Rogers and Schmittat (1997) provided a diagrammatical
overview of the stages in handwriting production and the corresponding dynamics that
examiners may infer (see Figure 10.1).

It is the dynamic elements of handwriting production that forms the visual features of
handwriting that examiners focus on when gauging relative line quality. In particular
examiners may make observations regarding pen pressure (as evidenced by relative
indentation depth, relative density of ink deposits or relative width of the line), flying
starts or finishes (as evidenced by the tapering of the line trace caused by the
movement of the writing instrument as it comes in contact with, or leaves the writing
surface), pen drag (caused by the connection between strokes where the pressure
exerted on the page by the writing instrument is reduced) and smoothness (which
results from smooth acceleration and decelerations of the writing instrument over the
writing surface). It is these features, usually in combination, that are assessed to
determine whether one sample of writing was performed with greater or lesser skill
than another.

Under normal circumstances, if this stage in the method is resolved, the sample base
writing is considered to be close to ideal with reference to the amount and timing of
the writing. Usually the two or more sample writings share features that are unlikely
to result from a chance match. Under these circumstances there is support for the
proposition that one sample of writing is considered to have been simulated from a
population of writing similar to that from which the comparison sample was drawn.
This does not preclude however that the specimen writer may have disguised their
own writing consciously or that variation has occurred as a result of altered
neurophysiology (due to for example, illness or medication).

                  Abstract Motor                    Structural variants
                     Program                        Changes over time
                                                    Range of normal variation

                    Motor Buffer                    Relative speed
                  Parameterisation                  Space


                   Muscle Set


                                                    Writing surface
                    Movement of                     Characteristics
                  Writing Instrument                Ball rotation
                                                    Relative pen pressure
                                                    Relative speed
                           Imaging Substance        Pen tilt
                                Transfer            Pen up - pen down

                 Questioned Line Trace

Figure 10.1 A diagrammatical overview of the stages in handwriting production and
the corresponding dynamics, many of which may impact on the assessment of line
quality, that examiners may infer (Found, Rogers & Schmittat, 1997).

Questioned writings exhibiting greater skill relative to specimen writings

In some circumstances it may be possible to support the proposition that simulated
writings were not written by a specimen writer. This usually occurs under the
following conditions:
• the comparison material is comparable and has been sampled over an extended
period of time.
• the comparison material brackets closely the alleged time that the sample images
being compared to it were allegedly produced.
• the comparison material, without exception, displays poor line quality as evidenced
by tremor in the line, dysfluencies, pressure differentials uncharacteristic of normal
stroke formations and concatenations, and variations in these characteristics within
allographic forms.
• there is a sufficient quantity of comparison materials (ie. there is more than only a
few allographs or stroke combinations).

These types of characteristics within the comparison base writings are indicative of a
writer who lacks the skill to write fluently. Should the comparison base material
display these characteristics and the material being compared display line quality
indicative of a skilled writer then support may be expressed for the proposition that
the specimen writer did not write the questioned entries (see Figure 10.2).

  Figure 10.2 A sample of comparison base writings showing a poorly skilled writer
and questioned writings showing a significantly higher skill level. There is support for

   the proposition that the writer of the specimens is unlikely to have produced the
                                  questioned writings.

Questioned writings exhibiting lesser skill relative to specimen writings
Should the questioned writings exhibit a lesser skill than the comparison base
writings, but still share features in common with the specimen writings, then
authorship opinions are unlikely to be expressed (see Module 9).


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