Examination of Printed Documents

1. EXAMINATION OF PRINTED
DOCUMENTS
Session-6

2. PRINTERS
 Numerous types of computer printers are in use
today. Most printers fall into two broad categories
based on how the machine creates an image.
Impact printers are usually older machines with
mechanical parts, not unlike typewriters, that
“strike” the image onto paper. Examples include
thermal, daisy wheel, and dot matrix printers. Some
of these still use ribbon cartridges! These printers
suffer the same aging effects as typewriters and—in
certain cases—sometimes create unique tool marks
as artifacts of their mechanisms.

3.  Ink-jet and laser printers are examples of
nonimpact processes. The appearance of toner and
how it is adhered to the document may assist the
examiner in individuation. For example, toner that is
improperly fused may indicate problems in a laser
printer.

4.  The combination of computerized font libraries with the
reliability of laser and ink-jet printing offers the forger a way to
create seemingly authentic documents that are either in the
style of an original or intended to be copies of an original.
However, the forger may not identify the correct typeface—
many look very similar, and kerning or other computer printer
idiosyncrasies may result in a printed document that is not in
fact identical to the authentic one. The technique of
superimposition, using equipment such as the Foster and
Freeman
 VSC 6000, can identify these close calls by showing the
minute physical displacements when the questioned
document is superimposed on the authentic one. This is
illustrated in Figure

6.  Figure shows the dot pattern of a 9-pin dot-matrix printer;
the dot pattern serves to identify the dot-matrix printer.
The dot pattern is less discernible in the pattern produced
by a 24-pin printer or when a printer is set to “letter
quality” mode rather than draft mode. The numerous pins
that produce the dot-matrix characters can develop
defects. And in some cases, the defects can be
sufficiently unique to connect a questioned text to a
specific dot-matrix printer. But these pin defects develop
far less frequently than do the defects that develop in the
typeface characters of impact manual typewriters and
impact electric typewriters.

8.  Figure shows the imprint made by an ink jet printer. The
fast drying ink is ejected onto the paper from tubes in the
printer’s ink cartridge. Note the feathered edges of the
various letters caused by spattering of the ink on impact
with the paper. The paper’s surface texture can affect the
amount of spattering. This spattering is one feature that
helps to identify the ink jet printer.

9. B

10.  Figure was produced by a laser printer. The laser printer product is
similar to that produced by a plain paper office copy machine. An
image of the laser’s keyboard generated text is electronically created
on the printer’s drum. Powdered toner sticks to the drum where the
electronic image was formed. The toner image is transferred to plain
paper and the toner is briefly heated so that the toner fuses to the
paper: the same process as a xerographic office copy machine.
Viewed under the microscope, the printout of the laser printer is very
similar if not identical to that of an office photocopy. Thus, it can be
difficult to discern the difference between an original document just
produced on a laser printer and a photocopy of that original.
Experience to date has shown that ink jet printers and particularly
laser printers develop few of the unique imprint defects that can
connect a questioned text to one specific make or individual printer.
Also, ink jet printers and laser printers have the built-in capability of
printing a multitude of different character designs. This feature rarely
permits an identification of the printer’s manufacturer. In summary,
successful identification of a specific make of ink-jet printer or laser
printer, or the connecting of a questioned document to a specific ink-
jet printer or laser printer is seldom possible.

11.  Screen shot from Foster and
Freeman VSC 6000 showing
superimposed authentic and
forged printing. The documents
are aligned with the word Trustee in the center.
Although it looks identical in both, as the text gets
displaced from the centered word, the
misalignments become clear

13.  The internal paper transport mechanism of some copiers can
produce indentations and other markings on the paper as it is
being transported through and out of the machine. These
class characteristics, when discernible, can in some cases
provide an identification of the copier’s manufacturer if the
examiner has appropriate reference files. The copy machine
can also produce unique and identifying defects on the
photocopies it generates. These individual characteristics
(defects) can be created by high volume use, by the careless
removing of jammed paper (producing scratches on the drum),
lack of normal maintenance and repair, and by infrequent
cleaning of rollers, drum, corona wires, and platen. These
individual characteristics can appear as black or white lines
across the paper, as tiny black specks called “trashmarks”, as
smudges, and a variety of other flaws.

14. FAX MACHINES
 Fax machines and “all-in-one” machines employ
technology similar to that found in printers.
However, fax machines usually stamp documents
with a code called the transmitting terminal
identifier. This label is often found at the top or
bottom of a fax printout. Analyzing the typestyle of
the TTI can help examiners identify the correct
machine.

15. PHOTOCOPIERS
 A printer may be shipped to the laboratory for analysis, but,
due to size and weight, a photocopier is usually sampled in
place. Because it may take several copies for the drum to
make a complete revolution, noting the order in which the
sheets of an exemplar were produced is desirable.
 Inside the copier, a camera captures the image of the
document that is transferred to a cylindrical drum. The drum
has a static-charged, light-sensitive surface.
 When exposed to light from the image of the document, areas
of more or less static electric charge (which will correspond to
light and dark areas on the copy) are created. The drum is
then exposed to a toner that will adhere to the surface of the
drum in proportion with the amount of static electric charge.
Then the toner is transferred to a piece of paper and fused in
place by a heating element

17.  If the examiner finds that a combination of similar defects
exists between a questioned photocopy and an exemplar
photocopy made on a suspect copier, then there might be
sufficient evidence to conclude that both were produced
on the same copier. The examiner must always be
absolutely certain that the submitted questioned
photocopy is in fact the photocopy in question — that it is
not a second generation photocopy made from the
original questioned photocopy on an intervening copier.
The intervening machine could introduce misleading
trash marks and other defects that are not related to the
investigation. This same caution applies to the evaluation
of the submitted exemplar Specimens.

18.  Color copy machines have invited the counterfeiting
of paper money, stamps, bank checks, driver
licenses, or any documents that will serve the
purposes of thieves. Color copies can be identified
as such by a microscopic examination of the image.
The microscopic examination will disclose the
overlaying pattern of the various single colors that
in turn produce the various hues in the color image.