Computer printouts and fax• Compare markings on a QD to an exemplar• Transitory patterns may arise from debris and other

materials• TTI- tranmitting terminal identifier- on top of each fax

page is in a different font determined by the sending machine and type set from text.

• Alterations detected if TTIs reveal significant characteristics distinguish it from genuine TTI

• TTIs number of characters, style, position in the header can all be evaluated through comparison to a collection of TTI font database maintained by the ASQDE

Differences Observed in Fax Lettering as Wear Increases

Class characteristics of printouts

• Printing technology, type of paper and toner• Toner chemical composition• Type of toner to paper fusing method• Microscopic and ID of organic and inorganic

components of toner• Results compared to databases on types of

machines• Narrow down to manageable number for

subsequent comparison to exemplar printouts

Model determination based on printouts

• Requires extensive analysis of printer tech and type of ink used

• Impact or non impact printers– Non-impact include ink-jet and laser printers

– Impact type include thermal and dot matrix printers

– All have characteristic ways of printing with shapes, toner differentiation and applications easily determined with low power microscope to narrow possibility of model type

Alterations, Erasures and Obliterations

• Common erasures include india rubber eraser, sandpaper, razor blade or knife obliterations

• Disturbance of upper layer of fibers on paper detected with microscopy using direct or oblique lighting

• Chemical erasures use oxidizing agents on ink – detected by discoloration on treated area

• UV or IR can reveal chemically treated portion

Infrared luminescence• Some inks reradiate IR known as

IR luminescence• Differences in the luminexcent

properties of the inks observed if altered

• Can also be used to reveal writing that has been erased as invisible residues of writing may remain in paper

• Also differences exist in ability of inks to absorb IR. Distinguish inks of dissimilar chemical composition

Obliteration

• Intentional obliteration - overwriting or crossing out : seldom used for fraudulent purposes as it is obvious

• Same ink- difficult to tell from original

• If two inks are different photo with IR sensitive filme may reveal the original writing.

IR Device Used for Questioned Document Analysis

IR photographic detection of obliteration

White Out Obliteration

Case File: Obliterated Address

Top image: normal lighting

Middle image: reflected infrared

Bottom image: infrared luminescence

Charred documents

• IR photography useful in revealing contents of charred documents

• Oblique lighting can also be used to contrast the writing vs charred background

Detection of charred document contents using oblique lighting

Digital image enhancement

• Visual quality of digital picture is improved or enhanced

• Digitizing- image is stored into memory by scanning an image with flatbed or digital camera and converting the image into digital intensity values called pixels (picture elements)

• Image editors (Adobe photoshop) used to adjust contrast, color, etc.

Digital image enhancementusing Adobe Photoshop screen and exclusion

Indented writings

• Partially visible depressions appearing on a sheet of paper underneath the one on which the visible writing was done

• Depressions due to application of pressure on the writing instrument and appear as a carbon copy of a sheet if carbon paper had been inserted

• Like my check book