forgery and counterfeiting questioned documents 2
TRANSCRIPT
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Forgery and Counterfeiting
Questioned Documents 2
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Criminal Forgery
• Multi-billion dollar business
• Both forensic techniques and detection methods have become very sophisticated
• FBI white collar crime (now along with terrorism) is largest division
• Includes checks, credit card receipts, insurance policies, etc.
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Criminal Forgery
• Also clothing, music, electronics, jewelry
• Product counterfeiting estimated to be 5%-7% of world trade– $500 billion each year
• Rampant in the Far East– Taiwan, Singapore, Indonesia
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Criminal Forgery
Open air bazaar in Ankara, Turkey.
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Detecting Forgeries
Lighting effects– Oblique angles– UV lights
An “invisible” identification marking that is only visible under ultraviolet light.
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Detecting Forgeries
• Chemical analysis– Iodine treatment (same as fingerprinting)– pH testing– Ink analysis– UV detection
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Detecting Forgeries
• Obliterations– Often involves physically erasing marks or scraping ink
off paper’s surface
• Methods disturb top layers of fiber from paper– Can usually be seen with oblique light under a
microscope
• Chemical obliteration– Certain chemicals can react with ink to make it colorless– Can also be seen with certain techniques
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Identifying Paper
• Nature of paper– Actually a blend of wood pulp, cotton or other
materials– “Bond paper”
• 25-50% cotton
– Watermarks• Created by reducing number of fibers
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Identifying Paper
• Forensics is interested in:– Raw material– Color– Density– Watermarks– Dyes/bleaches– Fluorescence– Thickness
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Chromatography
• Scientific technique used extensively in the identification of chemicals
• A forensic scientist may be able to link the presence or absence of chemicals to a suspect
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Chromatography
• Essentially the separation of chemical mixtures and substances
• Technique depends on the fact that different chemicals will be absorbed at different rates by another chemical selected to separate the unknown mixture
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Thin Layer Chromatography
• Glass slide is coated with a thin layer of gel• Small amounts of unknown sample are
dotted near the bottom of the slide• Slide is then placed in a liquid so level of
liquid reaches just below the dots on the slide
• As gel absorbs the liquid, it “climbs” up the slide and separates the unknown sample
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Gas Chromatography
• More recent technique– Requires computer assistance
• Unknown mixture is vaporized by heat inside chromatograph.
• Vaporized mixture is forced by a non-reactive gas along a narrow, coiled tube
• Different components in gas flow at different speeds and are detected at the end of the tube
• Especially useful in blood alcohol tests, ID of street narcotics and in fire investigation
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Gas Chromatography
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Gas Chromatography
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Paper Chromatography
• Uses a vertical piece of filter or other absorbent paper
• Unknown substance is applied near the bottom of the paper
• Paper is hung with its end in a liquid and allowed to soak
• As the liquid is absorbed by the paper and rises, it will carry some or all of the unknown substance with it creating the chemical “fingerprint”
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Paper Chromatography
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Gas Chromatography
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Paper Chromatography
Paper chromatogram indicating the natural (and possible artificial) dyes of a marijuana sample