Forensic Science

4 th Amendment The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.

The Document Examiner Usually asked to determine if a document is ‘authentic’ Questioned Document – any handwritten or typewritten document whose source or authenticity is in doubt Takes years of training and experience to become good at comparing characteristics The uniqueness of handwriting can be considered individualized evidence

Comparing Handwriting – General Style First learning to write involves copying a style from a teacher Page 556 Figure 16-1 At this early stage handwriting of different students is very similar As a person grows up they start personalizing their handwriting styles without even thinking about it

Comparing Handwriting - Variations Variations expected in: Angularity, slope, speed, pressure, letter and word spacings, relative dimensions of letters, connections, pen movement and writing skill Also differences in WHERE someone writes on the paper (how close to the margins, how far above the line, etc) Each type of variation may not be unique to a person, but the combinations of variations is How many “matches” between evidence and a reference sample it takes to make a definite authentication depends on the scientist

Challenges to Comparing Handwriting The biggest challenge is when not enough reference or “known” samples are received for comparison. Another frequent problem is when questioned documents only contain a few words or those words are carefully written to have fewer of the writer’s individual characteristics Frequently done with threatening letters, etc When there is enough writing for comparison, the attempt to hide individualizing characteristics may fail Page 557 Figure 16-2

Collecting Writing Samples Writing samples (exemplars): Should contain as many as the same words as possible Should be written on the same type of paper with the same utensil There should be enough exemplars to show the natural variations in the writer’s style. P 559 Figure 16-3 The exemplars should have been written around the same time as the evidence Ex: can’t compare writing from when a suspect was 12 to when he was 20

Getting an Accurate Exemplar The writer should sit comfortably at a desk or table and not be distracted. The writer should NOT be shown the questioned document. The writer should be given a pen and paper similar to those used for the questioned document. The exemplar should contain the same words or letter combinations as the questioned document. Should be written at least 3 times. Make writer write other things along with a signature. (like a check)

Comparing Typescript Documents The examiner may have to identify what brand of printer or fax, etc was used to produce a document If test samples need to be printed, usually around 10 are printed to show the machine’s characteristics

Comparing Photocopied Documents Comparisons usually involve looking at defect marks made by debris on the glass surface, inner cover or mechanical portions of a copier

Comparing Faxed Documents Most important to study and compare the header (Transmitting Terminal Identifier) P 562 Figure 16-4 Can be faked, but microscopic examination usually reveals the falsity Can use the header to determine the machine’s model

Comparing Computer Printed Documents When there is a suspect machine, comparisons of markings can help determine the origin of a questioned document When there is not a suspect machine, work can be done to identify the printer model used: Examine the toner with a microscope Find the chemical compounds within a toner Find the type of paper used The method used to apply the toner to the paper EX: ink-jet, thermal transfer, laser printers, etc

Comparing Typewritten Documents Finding the make and model of typewriter used: Compare to databases of what typeface is used, what style of letters, etc Finding out if a suspect machine produced specific evidence: Does the normal wear and damage to the machine match? Ex: are the letters misaligned identically Full word-for-word examples can be compared to see if the defects match (p 563 Figure 16-5) The ribbon can be studied to find the portion of the ribbon used to type the evidence

Alterations of Documents - 1 Change after their original preparation Erasures: Trying to erase a part of a document Disturbs the surface fibers of the paper (visible under a microscope or under “side lighting”) Obliterations Trying to remove a part of a document chemically Usually evident under a microscope. IR or UV lighting usually shows where a document as been altered this way

Alterations of Documents - 2 Adding to a document: Can be exposed by shining a blue-green light on the document. Many inks release differing amounts of IR light in these situations. You can see the difference in the inks. Different inks also absorb IR light differently, which can expose different inks P 566 Figure 16-7 P567 Figure 16-8

Alterations of Documents - 3 Crossing things out or overwriting: Usually not done because of its obviousness Can hide the original writing if the inks are similar enough Analyzing charred documents: Reflect light off of the document surface to contrast the writing – p 569 Figure Digitalizing is commonly done to investigate or enhance documents - p 570 Figure & p 571 Figure 16-12

Indented Writings Partially visible indents on a piece of paper that was underneath the written on paper. These indents can contain incriminating evidence, even if the original written document can’t be found Toner powder can be applied across a page to find indented writings P 572 Figure 16-3

Ink Comparisons The composition of dyes can be compared by: Visible microspectrophotometer Thin-layer chromatography (TLC) – shows the dyes broken into their components by how fast they move up a column of paper Can be compared to the US International Ink Library Describes not only type of dye but when it was produced, etc

Paper Comparisons Paper is usually made from cellulose fibers from wood and fibers from recycled paper products Can examine and compare: Chemical makeup of paper General appearance Color Weight Watermarks Read Forensics at Work p 558