1 Forensic Science Questioned Documents Document Analysis

2 Paper Chromatography with Ink Two samples of black ink from two different manufacturers run using paper chromatography.

Retention Factor (R f ) )This is a number that represents how far a compound travels in a particular solvent )It is determined by measuring the distance the compound traveled and dividing it by the distance the solvent traveled.

4 Scientific Equipment )Gas chromatograph--separates mixtures on the basis of their distribution between a stationary liquid phase and a moving gas phase. )The written record of the results is called a chromatogram. A typical one will show a series of peaks, with each representing one component of the mixture. )The time required to go from the injection out of the column is known as the retention. This allows identification of class characteristics.

5 Scientific Equipment )Mass spectrometer--an instrument that connects to the gas chromatograph. The substance to be identified is exposed to a beam of high-energy electrons causing the molecules of the sample to lose electrons and to acquire a positive charge. )These positively charged molecules decompose into numerous fragments. These fragments then pass through an electronic or magnetic field where they are separated according to their masses. ) The unique feature of mass spectrometry is that no two substances produce the same fragmentation pattern, thus producing individual characteristics.

6 What are some ways documents can be altered? )Means: eraser, sandpaper, razor blade, knife, bleach, etc. )Two types of erasures: mechanical and chemical )Mechanical: rubbing ink/pencil with abrasive material that disturbs the paper fibers )Chemical: use ink eradicators like sodium hypochlorite in bleach

7 How can they be detected? Detection: )Microscope: may reveal erasure )Infrared luminescence: some inks if exposed to blue- green light will absorb the radiation and reradiate infrared light )Infrared photography: reveals contents of documents obliterated or charred (Obliteration- blotting out or smearing over writing or printing to make original unreadable) Digital image processing: visual quality is improved or enhanced

8 How can paper be identified? )Weight )Color )Water marks: translucent mark in paper; specific to manufacturer and changed periodically; can establish age and possible location of store selling it )Age )Fluorescence in UV light

9 Pencils )Lead )Hardness Scale-- a traditional measure of the hardness of the "leads" (actually made of graphite) in pencils. The hardness scale, from softer to harder, takes the form..., 3B, 2B, B, HB, F, H, 2H, 3H, 4H,..., with the standard "number 2" pencil being of hardness 2H.

10 Forgery )Check Fraud )Forgery )Counterfeit )Alterations )Paper Money )Counterfeit )Identity )Social Security )Driver’s license )Credit Cards )Theft of card or number )Art-- imitation with intent to deceive )Microscopic examination )Electromagnetic radiation )Chemical analysis

11 Codes and Ciphers )Codes--letter combinations or symbols used to represent words or concepts )Interception from terrorists and other war enemies )Ciphers--a message in which letters or symbols replace the actual letters in the message.

CRAZY CRIMINALS According to Point of View, a magazine published by the Alameda county District Attorney’s office, a guy walked into an Oakland bank and handed the teller a note reading, “this is a stikkup. Hand over all yer money fast.” Guessing from this that the guy was no rocket scientist, the teller replied, “I’ll hand over the cash as long as you sign for it. It’s a bank policy that all robbers have to sign for their money.” The guy thought this over, then said “Uh, I guess that’s OK.” He signed his full name and address. That’s where the cops found him a few hours later.

13 Used as Evidence 1. Class characteristic--the type of ink may have similar characteristics at the primary and/or secondary crime scene, on the suspect or on the victim. Handwriting may be used to include or exclude a suspect. 2. Individual characteristic--With document analysis, it is difficult to identify to an individual characteristic except with typewriter or printer specific marks.