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Crime Labs

Forensic Analysis Units

Questioned Document Unit

Handwriting and Hand Printing

The majority of the cases submitted to the questioned document unit involve the examination and identification of handwriting and hand printing. A systematic side-by-side comparison of questioned and known writing using appropriate lighting and magnification is performed. Handwriting/printing cases include: forged and altered checks, threatening letters, bank robbery notes, bomb threats, prescriptions, medical records, contracts, and graffiti. The questioned document unit has been asked to examine writing on walls, cars, mirrors, doors and other surfaces.

Ink Differentiation Areas other than handwriting and hand printing identification are also considered in the examination of questioned documents. Ink differentiation is used to detect alterations, erasures, and material changes in documents. Ink may be differentiated nondestructively with a video spectral comparator (VSC-1). Physical and chemical properties of two different inks will cause differing results when examined using the alternative light sources and filtering techniques available with the VSC. Another method is thin-layer chromatography of inks this is a destructive chemical testing used to compare formulas of ink on alleged altered documents.

Ink differentiation by tlc.

Instruments

Instruments used in the questioned document section include: stereo microscope, light microscope, video spectral comparator (VSC-1), electrostatic detection apparatus (ESDA), and photographic filters.

Ink differentiation by spectral analysis.

Typewriting

Cases containing questioned typewriting are often submitted to the questioned document unit. Milwaukee, Wisconsin is the birthplace of the typewriter. In this age of computers, laser and ink jet printers, one might ask, "Who cares about typewriters?" Forged checks, anonymous letters, even bomb threats have been created with typewriters. Typewriter defects have been used to identify a threatening letter with typewriting on a carbon film ribbon found in a suspect's home.

Linking document to typewriter    a. document    b. ribbon    c. character        (reversed)

Paper

Most questioned documents are written on paper. Examination of the physical and chemical properties of papers is often of identification value. Watermarks are the designs impressed on paper by the raised pattern of the dandy roll in paper making. Better grades of business papers use watermarks that usually consist of the company name or logo. Watermarks can often be dated by the manufacturer even if no formal date code is incorporated, by design changes.

Photocopies and Photocopiers

Photocopiers may produce identifying marks that enable the manufacturer to be established. Photocopied documents may be identified with a particular machine through defects reproduced on copies from the glass platen, lens, or drum of the particular machine. The type of photocopying process used may also be established.

Computer 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 when appropriate instrumentally and non destructively with a video spectral comparator (VSC).

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