Chapter 16: Document and Voice Examination Forensic Science Chapter 16: Document and Voice Examination

Questioned Document Any document about which some issue has been raised or that is the subject or an investigation source or authenticity is in doubt May include writings on walls or other objects

QD success Based on applying knowledge gathered through years of experience and training. Comparison-based Need known writings As unique as fingerprints

General style Learned in school as we copy letters For young learners, handwriting is very similar. Changes by time and locale As the learner gets better at writing and the process becomes subconscious, they start to develop their own style and writing becomes more unique.

Variations Expected in Slope Speed Pressure Letter and word spacing Relative sizes of letters Connections Pen movements Writing skill Finger dexterity

Variations from habits Margins Spacings Crowding Insertions alignment

Other variations Spelling Punctuation Phraseology grammar

comparisons Must be based on many characteristics

Difficulties Only a few words Written to disguise Threatening letters Attempt may fail if the document is long Altered by drugs or alcohol

Exemplar An authentic sample used for comparisons purposes

Natural Variations Normal deviations found between repeated specimens of an individual’s handwriting or any printing device. Handwriting changes with age (but slowly) If a signature matches exactly, that points towards forgery by tracing.

Getting exemplars May be obtained by court order Handwriting samples are not protected by the fifth amendment Right to not incriminate yourself Doesn’t violate the fourth amendment Police need a warrant to search you or your property

Getting a good sample Let the writer sit comfortably without distraction. Don’t show them the QD or help them with spelling or punctuation. Use similar pen and paper to the QD. Use the same words as the QD

Getting a good sample Don’t tell them when to use uppercase unless necessary. Collect at least a page of exemplar. Have them repeat the writing three times. Have them write signatures with other text – such as a check. Have the QD examined before taking exemplars.

Comparing typewriters Determine make and model databases Compare to suspect machine Wear and tear Letters are too high or low Letters are off to one side Letters slant

Comparing printers, copiers, and faxes Make and model Compare with suspect machine Markings produced by machine Debris in machine

Erasure The removal of writings, typewriting, or printing from a document. Either chemical means or an abrasive instrument.

Erasures Upper fibers are disturbed. Can be see with a microscope or oblique (side) lighting. Can’t always determine what was erased.

Infrared luminescence Some dyes emit infrared light when exposed to blue-green light. Used to detect alterations made with a different kind of ink. Used to reveal writing that has been erased.

Obliteration The blotting out or smearing over of writing or printing to make it unreadable. Difficult to recover if the same ink is used. Different inks may be detected using infrared photography.

Charred document Has become darkened and brittle through exposure to fire or excessive heat. Can decipher using infrared photography or light at different angles.

Digitizing Storing an image into a computer’s memory. Scanner Digital camera Digitized images can be edited using a program such as Adobe Photoshop ® Lighten/darken Color Contrast See color plates between pages 478 and 479

Indented writings Impressions left on papers positioned under a piece of paper that has been written on. Readable under oblique lighting Electrostatic detection The paper is charged and toner is applied. The toner sticks to the indented writings, making them visible.

Ink analysis Chromatography is used to separate ink into individual dyes. The Treasury Department is compiling a database of inks. Can prove backdating if the dye used was not yet available. Tagged ink – produced using a different chemical tag each year to allow precise dating.

Paper analysis General appearance Weight Color Watermarks Fiber identification Additives, fillers, and pigments

Chromatography More notes coming soon…..

Sound spectrograph Converts speech into a visible graphic display developed in 1941 at Bell Telephone Laboratories Used during WWII Now widely accepted as evidence in court

Voiceprint Pictorial representation of the frequency, duration, and amplitude of human voice sounds Used for identification

Body parts involved in speech Brain Controls speech process Lower respiratory Tract Trachea, lungs, diaphragm Used to supply the breath stream Vocal cords Used to modulate breath stream

Vocal Cavities Articulators Nasal (nose), oral (mouth), pharyngeal (throat) Used to select and suppress overtones Articulators Lips, teeth, tongue, jaw, soft palate Used to vary the vocal cavities

Spectrogram (voiceprint) Frequencies are converted into electrical energy and recorded on special paper. Shows Time (horizontal axis) Frequency or pitch (vertical axis) Intensity or loudness (darkness)

Computerized voiceprints Easier analysis Allows high quality playback

Categories of identification Positive identification – more than 20 matching speech sounds Probable identification – more than 15 matching sounds and no unexplained differences Possible identification – more than 10 matching sounds and no unexplained differences Inconclusive decision – usually from poor recording

Possible elimination – 10 or more sounds that do not match Probable elimination – 15 or more sounds that do not match Positive elimination – 20 or more sounds that do not match