Hi monroe22,
"Is it possible to identify printout text or images as indisputably
done on a specific printer?"
Briefly, "yes", but it is easier to do with lasers rather than inkjets
because laser printers leave more physical marks on the paper.
However, matching dot-to-dot spacings to a specific inkjet printhead
cartridge is possible. Forensic Scientists are trying to keep up with
the ever improving printer technology - matching a document to a
modern printer is not as simple as it once was when typewriters were
the printer of choice, but it is possible.
LASER: ANALYSIS OF MARKS ON PAPER, OPTICS & TONER:
Photocopiers and Laser Printers:
"There are many ways to match a page back to a photocopier or laser
printer. Since, as shown above, the processes are similar, the
methods used to match a page back to its origin, printer or copier,
will also be similar.
The paper itself can yield many clues. Look for marks from the belts,
pinchers, rollers and gears that physically move the paper through a
machine."
"Toner can have unique characteristics in its chemical composition.
Also, look at how the tone was placed on and fused to the paper.
Toner may clump up on the drum, tranfering blobs of toner at a time to
the printed page."
"Marks on the optics (glass platen, lenses, mirrors) used to transfer
or create an image on paper might contain unique defects (such as
scratches) that will render anomalous markings on the printed page."
http://home.earthlink.net/~thekeither/Forensic/page4.htm
INKJET: ANALYSIS OF DOT QUALITY:
ACCN: L'Actualité chimique canadienne - Canadian Chemical News [illustrated]:
"Forensic chemistry is analytical chemistry applied to crime scene
analysis, and it usually deals with chemical residues, wherever they
may be found -- in fingerprints, in blackened bowls from a fire, in
wildlife, even in your ink-jet printouts. Learn more from our cover
features beginning on p. 12."
"The Case of the Burnt Bowls or what you need to know to be successful
in forensics."
by James Ford
Page 8: Figure 2. "Dot quality for a given printer, printing
ink/substrate or even ink jet printhead can be accurately quantified
in terms of several unique parameters, e.g. area roundness, axis
ratio, etc. More specifically one can also measure variations in
dot-to-dot spacings (as illustrated on the left) which in ink jet
printing provides a unique signature for every printhead cartridge,
since small out of specification variations between individual ink
channels can be resolved."
http://www.accn.ca/accn2001/october2001/ACCN%20OCTOBER%20Features.pdf
INKJET: ANALYSIS OF CARTRIDGES & NOZZLES:
Evidential Value from Ink-Jet Printers:
Stephen Philip DAY, Lee SHUFFLEBOTTOM
Forensic Science Service, Huntingdon, United Kingdom
"ABSTRACT: The widespread use of ink-jet printers has made it
necessary for document examiners to find a method of linking a
questioned document to an individual ink-jet printer. The
identification and characterisation of defects produced by ink-jet
cartridges provides a means of achieving this.
This study was primarily to investigate the physical nature of defects
in inkjet printers and show how printer outputs and printers can be
linked. Thus it was hoped to establish whether or not ink-jet printers
can be linked to their print-outs through their physical appearance on
the paper and if so to estimate the evidential value of any defects or
other physical features. By identifying such features it was hoped
that a protocol for the examination of this type of printer could be
developed.
Defects can be easily introduced into printouts by blocking the
electrical defects that control a particular print-head. The behaviour
of the defects thus produced is different for different types of
ink-jet print cartridges. By studying the behaviour of such defects it
is possible to devise a strategy for the examination to distinguish
between different printers. Not all nozzles get blocked with the same
frequency so if a particularly rare nozzle gets blocked then the
evidential value in linking that particular printer to the printout
will increase.
http://www.ies.krakow.pl/wydawnictwo/zzns/abstracts_xlvi.htm
INKJET: INK CHROMATOGRAPHY:
CLUE 3: Ink Samples
?Whose printer was it??
Ink from pens and printers can be identified using a technique called
ink chromatography. This technique is commonly used in cases where
documents or written notes are suspected of being fraudulent. In cases
where forgeries or false diary entries are suspected, ink
chromatography tests can identify the individual pens used to write
letters in the questioned document.
Ink chromatography relies on the capillary action resulting from
surface tension in liquids. A solvent is drawn up through a small
sample of ink which dissolves into the solution and travels up the
substrate (paper or coated microscope slides). As the ink rises
through the tiny spaces in the substrate, different sized molecules in
the various dyes separate and spread out, creating a type of
?fingerprint? for that particular ink. Crime prevention agencies all
over the world maintain databases of the thousands of inks made every
year to assist crime scene investigators in identifying virtually any
type of pen or ink-jet printer ink, laser printer or photocopier
toner.
http://www.abc.net.au/science/forensic/teachers-forensic-science.pdf
"Ink chromatography relies on the capillary action resulting from
surface tension in liquids. A solvent is drawn up through a small
sample of ink which dissolves into the solution and travels up the
substrate (paper or coated microscope slides). As the ink rises
through the tiny spaces in the substrate, different sized molecules in
the various dyes separate and spread out, creating a type of
'fingerprint' for that particular ink. Crime prevention agencies all
over the world maintain databases of the thousands of inks made every
year to assist crime scene investigators in identifying virtually any
type of pen or ink-jet printer ink, laser printer or photocopier
toner."
http://www.abc.net.au/science/forensic/clue_3.htm
Additional Links:
Ink Jet and Laser Printers:
"Ink jet and laser printers are common components of personal computer
systems used in homes and offices today. Typewritten documents are
being replaced by ink jet and laser printed documents. It is often
necessary to identify the printing method used to produce a disputed
document and to differentiate it from other printing methods. Ink jet
and laser printed documents are examined physically, microscopically,
and in some cases chemically with thin-layer chromatography."
http://www.doj.state.wi.us/dles/crimelabs/qd.asp
"Physical evidence can be marks left... by printers and copiers."
http://www.mfrc.ameslab.gov/FAQ_Forensic_Science_Student.htm
"Paper and inks, and handwriting analysis are forensic science
disciplines under the umbrella "Questioned Documents". Writing
instruments, typewriting, photocopying, computer printers, computer
disks, forgery, gambling machinery, rubber stamps, and the dating of
documents are also disciplines under Questioned Documents."
http://www.virtualmuseum.ca/Exhibitions/Myst/en/game/struggle/clue2.phtml
I hope this helps with your enquiry. If you have any questions, please
post a clarification request before closing/rating my answer.
Interesting topic.
Thank you,
hummer
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