Introduction
raditionally,
a large proportion of business letters were typed on manually
operated typewriters. During the last forty years, technology
has transformed the way in which not only businesses but also
domestic users produce documents, to the point now where the vast
majority are computer generated.
In typebar typewriters, when a key is depressed, a series of levers
cause the typebar to move and rotate causing that part 
bearing
the typeface to strike through an inked ribbon onto paper held
by a platen. Therefore the style of the typeface is fixed and
is liable to develop faults. Two main variants of this were developed
during the 1960's and 1970's - the so-called golfball and daisywheel
typewriters; in each case the typeface was present on a single
removable typing element. This allowed the style of the typeface
to be changed easily by inserting a typing element of a differing
typestyle. Starting in the 1980's computer based word processor
systems e.g. laser printers and ink-jet printers became more and
more widespread, becoming progressively cheaper and available
to more people.
The
Technique
The
examination of typed and word-processed documents is based upon
the same general principles:
- Identify
the means of production of the disputed documents; for example,
was it typed on manual typewriter, a single-element typewriter
or was it produced in an ink-jet printer or a laser printer
- Whether
there are any
features of the typing on the disputed document that can be
linked to other documents of known origin or to particular typewriters
or printers. For instance damage caused by wear and tear and
heavy use can produce imperfect typescript or printer output.
- Typewriter
ribbons can also be examined. This particularly applies to ribbons
which are intended to be used only once and then discarded,
and to correction ribbons
- As
a result of these examinations the expert can give an opinion
as to how likely it is that a particular machine was used to
type (or print out) a suspect document.
