Forensic Science Unit 7: Questioned Documents and Chromatography

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Evidence. 1. Class characteristic—ink analysis, paper analysis, most handwriting analysis. 2. Individual characteristic--With document analysis, it is difficult to identify to an individual characteristic except with typewriter or printer specific marks.. ID: 718431 Download Presentation

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Forensic Science Unit 7: Questioned Documents and Chromatography




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Presentations text content in Forensic Science Unit 7: Questioned Documents and Chromatography

Slide1

Forensic Science

Unit 7: Questioned Documents and Chromatography

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Evidence

1. Class characteristic—ink analysis, paper analysis, most handwriting analysis

2. Individual characteristic--With document analysis, it is difficult to identify to an individual characteristic except with typewriter or printer specific marks.

Slide3

Questioned Documents

Involves the examination of handwriting, ink, paper, etc. to ascertain the source or authenticity or detect any changes.

Examples include letters, checks, licenses, contracts, wills, passports, suicide notes, receipts, etc.

Topics

Handwriting analysis

Ink (and pens)Paper (and pencils)ForgeryCodes and Ciphers

Slide4

Questioned Documents

Forensic Document Examiner--involves the analysis and comparison of questioned documents with known material (exemplar) in order to identify whenever possible, the author or origin of the questioned document.

Unfortunately, no federal licensing exists.

May also be asked to determine if changes have been made.

Graphologist--attempts to predict character traits (personality) from handwriting examination

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History

Led to the conviction (and execution) of Bruno Hauptmann in 1930 based on ransom note handwriting.

Has not always been accepted by the courts.

In 1999, the US Court of Appeals determined that handwriting analysis qualifies as “expert testimony” and is admissible provided it follows scientific guidelines.

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Handwriting

Everyone has a unique handwriting style despite variations that occur due to mood, age, and hurriedness.

Handwriting analysis involves two phases:

The hardware--ink, paper, pens, pencils, typewriter, printers

Visual examination

Most frequently requested type of document analysisThere are 12 characteristics that are commonly examined. (RM pages 33-35)

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Line quality

Line quality—do the letter flow or are they deliberate

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Spacing

Spacing of words or letters—what is the average

space

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Size Consistency

Ratio of height, width, and size of the letters—are they

consistent

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Continuous

Lifting pen—does the author lift his pen between

words

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Connecting letters

Connecting strokes—how are capital letters connected to lowercase

letters

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Line habits

Strokes to begin and end—where do they letters begin and end on the page

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Pen Pressure

Pen pressure—how much pressure is applied on the up and down stroke

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Slant

Slant—do the letters slant left or

right or variable

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Letters Complete

Are letters completely formed?

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Cursive or Printed

Are letters cursive, printed, or both

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Fancy curls or Loops

Fancy writing habits—unusual loops or curls; unique styles

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Diacritics

Placement of diacritics—crossing t’s and dotting i’s

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Handwriting Analysis

Goal is to detect forgeries (documents made, adapted, or falsified in an attempt to deceive someone)

“ACE”

Analysis of the “

knowns

” with a determination of the characteristics found in the known .Exemplars (letters, diaries, cards, personal notes)Analysis of the questioned or unknown writing and determination of its characteristicsComparison of the questioned writing with the known writing.Evaluation of the evidence, including the similarities and dissimilarities between the “questioned” and “known” writing.

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Obtaining Handwriting Samples

The subject should not be shown the questioned document.

The subject is not told how to spell words or use punctuation.

The subject should use materials similar to those of the document.

The dictated text should match some parts of the document.

The subject should be asked to sign the text.Always have a witness.Repeat with the non-writing hand.Samples should be both requested and collected.

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Biometric Signature Pads

Recognizes your signature based on speed, pressure, and rhythm of signing.

Slight

differences can be detected.

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FISH

Forensic Information System for Handwriting

Database for handwriting used and maintained by the Secret Service.

Eliminates subjective opinions.

Has been used to verify that no two individuals pen their words exactly the same way.

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Shortcomings

Standards aren’t always good. Sometimes the standard for comparison is a forgery as well.

Effects of mood, age, drugs, fatigue, and illness on handwriting aren’t always predictable.

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Linguist

Experts that look at the linguistic content (the way something is written) of a questioned document.

Language that is used can help to establish the writer’s age, gender, ethnicity, level of education, professional training, and ideology.

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Forgery or Fraud

A

forgery

is the

a

ct of falsifying something with the intent to deceive someone.Fraud is committed when you profit (some material gain) from a forgery.

Slide27

Check Forgery

Checks can be forged by:

Ordering someone else’s checks

Directly altering a check

Intercepting someone’s check, altering it, and cashing it.

Creating forged checks from scratch

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Check forgery

Ways to prevent

Checks printed on chemically sensitive paper

Use large font size

High resolution borders that are hard to copy

Print in multiple color patternsEnhanced fibers that glow under different lightsUse chemical washes that change colors when a check is altered.

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Ink

Chromatography--physically separate mixtures of gases, liquids or dissolved solids.

Types

Gas Chromatography

HPLC--high-performance liquid chromatography

TLC--thin-layer chromatography Paper Chromatography

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Gas Chromatography

Used to determine the chemical composition of unknown substances, such as the different compounds in gasoline shown by each separate peak in the graph below.

Paper Chromatography

Can be used to separate the components of inks, dyes, plant compounds (chlorophyll), make-up, and many other substances

Liquid Chromatography

Used to identify unknown plant pigments & other compounds.

Thin-Layer Chromatography

Uses thin plastic or glass trays to identify the composition of pigments, chemicals, and other unknown substances.

Examples of Chromatography

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Paper Chromatography with ink

Two samples of black ink from two different manufacturers run using paper chromatography.

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Retention Factor

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.

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Retention Factor

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Black Marker after Chromatography

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Gas Chromatograph

Separates mixtures

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. This allows identification of class characteristics.

Slide37

Mass Spectrometer

an instrument that connects to the gas chromatograph.

The substance is exposed to a beam of high-energy electrons.

F

ragments then pass through an electronic or magnetic field where they are separated according to their masses.

No two substances produce the same fragmentation pattern, thus producing individual characteristics.

Slide38

paper

Weight

Color

Water marks

Age (binding agents and chemical composition)

Slide39

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.

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Counterfeiting

When documents are copied with the intent to deceive.

The most common are traveler’s checks, bonds, and currency.

Counterfeiting on money is investigated by the Secret Service.

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Counterfeiting Prevention

US currency has specific features to make it difficult to counterfeit.

The number one feature is the special paper it is printed on.

Counterfeit detection markers contain iodine which reacts with fake money to turn blue-black. Claim to be 98% effective.

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1. portrait stands out and appears raised

2. there is micro printing on the security threads and portrait.

3. serial number is evenly spaced and same color as treasury seal

4. check letter and quadrant number

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5 and 6 Treasury and Federal reserve seals are sharp and crisp.

7. Red and blue fibers throughout and security thread.

8. federal reserve number and letter

Slide46

9. series

10. check letter and face plate number

11. watermark on right side

12.Colorshift from copper to green.

13. Clear background lines and detail

14. clear distinct border edge

Slide47

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.

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Code Breaking terms

Encipher (to encode)---to hide the message; top to bottom in a cipher key

Decipher (to decode)---to reveal the message; bottom to top in a cipher key

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Shift cipher

Simplest type of cipher.

Works by shifting the alphabet a certain number of places

There are 25 possible keys.

Slide51

Caesar Shift

Caesar simply replaced each letter in a message with the letter that is three places further down the

alphabet.

Slide52

Frequency Analysis

If you have got a

message you

want to crack, you can use frequency analysis.

In

other words, if the sender has tried to disguise a letter by replacing with a different letter, you can still recognize the original letter because the frequency characteristics of the original letter will be passed on to the new letters. Which letters are the most common in English?

Slide53

Frequency

ANalysis

Slide54

Frequency Analysis

T

hese

frequencies are averages, and E will not always constitute 12.7 % of all the letters in a text, and may not even be the most common letter.

The

longer the message, the more likely it is that will obey the average distribution shown above. However, there are exceptions to this rule.

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