Forensic Chemistry & Toxicology Questioned Documents PDF

FORENSIC CHEMISTRY & TOXICOLOGY QUESTIONED DOCUMENTS I. QUESTIONED DOCUMENT  Any handwritten/typewritten document having a questionable authenticity and subjected to a forensic document examination.  Any piece of evidence that...

FORENSIC CHEMISTRY & TOXICOLOGY QUESTIONED DOCUMENTS I. QUESTIONED DOCUMENT  Any handwritten/typewritten document having a questionable authenticity and subjected to a forensic document examination.  Any piece of evidence that bears symbols, marks or signs meant for a communication. QUESTIONED DOCUMENT EXAMINATION Conducted in:  Disputes involving SIGNATURES or HANDWRITING  Documents having a SUSPICIOUS AUTHENTICITY  Involves the application of scientific methods and principles for document examination COMMON TYPES OF QUESTIONED DOCUMENTS Wills Stamp Papers Cheques Passports Bank Drafts ID Cards Agreements Licenses Receipts Currency notes Laminated Documents Suicide notes Photocopied Documents CASES WHERE FORENSIC DOCUMENT EXAMINATION IS APPLIED Identity Theft Bank Robberies Forgeries Contested Wills Counterfeiting Extortion Suicides Medical Malpractices Homicides Stalking Fraud Title/Deed Lawsuits Kidnappings Contested Contracts METHODS OF QUESTIONED DOCUMENT ANALYSIS General Methods: NON-DESTRUCTIVE METHODS  Use of electrostatics and/or light for examining documents  Helps in determining any ink differentiations or indented impressions on the documentary evidence DESTRUCTIVE METHODS  Require removal of small samples of ink from the questioned documents 1. REVEALING TEXT FROM INDENTED IMPRESSIONS Can be visualized through the use of an Electrostatic Detection Device (EDD) such as the Electrostatic Detection Apparatus (ESDA) – Non-destructive Method Uses applied charges and toner to visualize areas of indented writing, making them visible to the eye. Principle: Indented areas of the document carry less negative charge than surrounding areas. This causes the toner to be attracted to these areas, revealing indentations that are present. Up to seven layers of paper beneath the original writings. 2. DETECTING ALTERATIONS, OBLITERATIONS, ERASURES AND PAGE SUBSTITUTIONS Detected through use of photography and other imaging devices that utilize ultraviolet and infrared wavelengths of light. Video Spectral Comparator (VSC) – Non-Destructive Method Can reveal writing that has been added with a different ink, or has been altered or removed. Principle: Exploiting variations in the way different inks respond to different wavelengths of light. 3. MICROSCOPY Erasing a document by any method disturbs the upper fibers of the paper. Changes are apparent when examined under a microscope. Although microscopy may reveal that an erasure has been made, it does not necessarily reveal the original writing that was present. 4. INFRARED LUMINISCENCE The process by which some inks reradiate infrared light when exposed to blue-green light. Can be used to prove that a document was altered with ink that differs from that used in the original document. Process: a document is illuminated with blue-green light and pictures are taken of the document using infrared-sensitive film. Any differences in luminescent properties of the ink indicate that different inks were used. 5. DETERMINING INDIVIDUAL DYE COMPONENTS OF INK Liquid Chromatography Identify the chemical composition of inks on a document. A small cutting from the questioned document is dissolved in a solvent and analyzed. Inks can be compared to the International Ink Library (US Database) Paper Chromatography 6. TYPEWRITTEN AND MACHINE-PRINTED DOCUMENTS Documents created on a typewriter or printed with ink jet, laser printers, fax machines and photocopiers may be sourced to a particular make or model, or even to a specific machine. Printing process used to prepare documents can also be identified. 7. SEALS AND STAMPS Questioned documents bearing rubber stamp impressions, embossed seals, watermarks, or other mechanically printed marks may be submitted for examination. 8. PAPER Features varying between different paper samples include: General appearance Watermarks Raw material Thickness Color Age Weight Fluorescence Density