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

2. 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

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

4. 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.

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

6. Variations from habits
Margins
Spacings
Crowding
Insertions
alignment

7. Other variations
Spelling
Punctuation
Phraseology
grammar

8. comparisons
Must be based on many characteristics

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

10. Exemplar
An authentic sample used for comparisons purposes

11. 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.

12. 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

13. 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

14. 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.

15. 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

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

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

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

19. 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.

20. 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.

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

22. 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

23. 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.

24. 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.

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

26. Chromatography
More notes coming soon…..

27. 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

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

29. 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

30. 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

31. 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)

32. Computerized voiceprints
Easier analysis
Allows high quality playback

33. 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

34. 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