Introduction

Question 1

Trace evidence analysis

Answer 1

Deals with the minute transfers of materials that cannot be seen with the unaided eye

Question 2

Principle based on trace evidence

Answer 2

Locard’s principle

Exchange is a two way process

Question 3

Properties of trace evidence

Answer 3

1. Small, usually microscopic material
2. Physical remnants of a past criminal activity
3. Cross-transferred between two parties
4. Can be presented in court as evidence
5. Indicate objectively the origin
6. Links suspects to victims, location or items

Question 4

Levels of Locard’s principle

Answer 4

1. Physical level
2. Contectual/ Situational level
3. Intelligence level

Question 5

What constitutes the physical level of Locard’s principle

Answer 5

Transfer and persistence

The shorter the persistence, the ease of transfer

Question 6

What factors constitute the physical level

Answer 6

Ease of transfer, retention ( how long does it stay ), persistence, affinity of material

Question 7

Material quantity transferred from source to target depends on:

Answer 7

The pressure applied
The number of contacts
Ease of transfer
Form of evidence
Surface area of item involved in the contact

Question 8

Direct transfer

Answer 8

Evidence is transferred from source to target with no intermediaries

From A to B

Question 9

Indirect transfer

Answer 9

Involves one or more intermediate objects

From A to C to B

Question 10

Persistence

Answer 10

Refers to how long it takes for transferred evidence to remain on a target until it further transfers, degrades or is collected

Question 11

Factors that affects evidence persistence

Answer 11

Evidence type ( states of matter)
Location of evidence ( type of substrate; porous/ non-porous)
Environment around the evidence(serene/ turbulent)
Time lapse from transfer to collection
Disturbance of/around the evidence location

Question 12

Situational level

Answer 12

Knowledge of circumstances and environment surrounding the crime

Evidence detection and identification

Significance of evidence

Question 13

Intelligence level

Answer 13

Knowledge about criminal behavior in single events or series

Challenges related to current trends in criminal behavior

Inter-agency information sharing

Question 14

Classification of trace evidence

Answer 14

1. Biological: e.g. body fluids, stains, tissues, vegetative matter
2. Non- biological: e.g. glass fragments, bullet fragments, explosive residues, paint chips, metal particles

Question 15

Types of trace evidence

Answer 15

Hair, fibers, paint, glass, soil, diatoms, blood, semen, DNA
Unusual: insects, match, grease, piece of paper, ash, seed, pollen, gum, cigarette

Question 16

Importance of trace evidence

Answer 16

1. Links a suspect to a crime/ a victim
2. Establish a sequence of events
3. Associate a murder weapon to a suspect / victim
4. Corroborate a victim’s account of circumstances surrounding assault
5. Links together a # of different criminal activities
6. Establish a high probability that there was contact b/n a victim, a suspect and a crime scene

Question 17

Properties considered on trace evidence analysis

Answer 17

Physical and chemical properties

Question 18

Physical properties

Answer 18

Identity of the substance doesn’t change
E.g. color, odor, boiling point, density, refractive index

Question 19

Chemical properties

Answer 19

Irreversible change into another substance with different physical properties
E.g. burning, chemical reaction

Question 20

Forensic application

Answer 20

Spectroscopy
UV/vis spectroscopy
Infrared spectrophotometry
Microscopy- light, fluorescence, polarized light
Chemical rxns- color, ppt formation, gas production, pH, solubility