Trace Evidence Analysis Flashcards Preview

Forensic BioScience > Trace Evidence Analysis > Flashcards

Flashcards in Trace Evidence Analysis Deck (32)
1

What evidence can be viewed under a microscope?

Light sources for objects and garments

2

What is the procedure of collecting trace evidence?

Characterisation and comparison
Assessment of significance
Safety of trace evidence (preservation/reliability)

3

What is trace evidence?

Very small amounts of material
Provides a link between suspect and victim/locus

4

What is Locard's principle?

Every contact leaves a trace

5

What are some examples of trace evidence?

Hair
Fibres (natural vs. artificial)
Glass
Paint sample
Fluids
Soil
Chemicals
Pollen
Seeds
DNA

6

What is a reactive trace?

Know something about the suspect, looking for links, i.e. suspect wearing red cardigan described by witness, look for that on victim

7

What is an inceptive trace?

Don’t know anything about suspect, find red fibres on victim, make connection. Find trace evidence don’t know who it’s come from actively link to suspect

8

What are different variables in types of material?

Amount of material- amount of material available for transfer
Nature and duration of contact, length of time of contact
Persistence of material- size, surface of receiving material, grooves on shoes
Finding the material- shaking, brushing
Evidence value of the material

9

What are the main ways to recover evidence obtained?

Shaking- shake garment to get material
Brushing- pocket lining brushing to remove trace material
Taping- recovers hair and fibres
Vacuuming- minute particles e.g., firearm discharge residue
Swabbing- small amounts of smeared material, e.g. blood, fluids
Hand picking- glass, leaves

10

What is the key information obtained from glass?

Shape, colour, thickness

11

What is the physical analysis of glass?

Refractive index (most common 1.5)

12

What is the chemical analysis of glass?

Scanning electron microscope (chemical characteristics, different radiation patterns)

13

What is a fibre?

Any long thin flexible solid objects with a high length to transverse cross-section are ratio

14

What are examples of natural fibres?

Animal, vegetable, mineral

15

What are examples of man-made fibres?

Organic, inorganic

16

How do you analyse fibres?

Taping
Low power microscopy
Cross-sectional shapes- thickness
Microspectrophometer
TLC (Thin Layer Chromatography)- removes dyes present in fibres
Infra Red Spectroscopy (particularly man-made fibres)

17

What is the hair made up of?

Medulla, Cortex, Cuticle

18

What is the Medulla?

Middle, collapse cells, sometimes difficult to see

19

What is the Cuticle?

Outside, scale cells

20

Where a possible sources of hair?

Clothing, bedding, sheets, weapon, car seats

21

Is the scaling the same or different in other mammals hair?

Different

22

What is the classification of hair?

Human, animal, body part it’s come from, determine race, any artificial alteration (e.g. wig, hair dye)

23

How do you examine dyed hair?

Use TLC

24

What are the phases of hair?

Annogen phase
Telogen phase

25

What is the Annogen phase?

Actively growing hair

26

What is the Telogen phase?

Hairs finished growing

27

What is the DNA issue with hair?

Can only obtain DNA evidence if root is obtained, only mitochondrial DNA can be collected if its from the body

28

What other information can hair give you?

Toxicology

29

How is evidence assessed for significance in terms of comparison?

How much analysis has been carried out, how much characterisation and comparison

30

What is the usefulness of rare evidence?

The less common the easier to produce a conviction

31

What are the issues with trace evidence?

Innocent sources accused due to secondary or even tertiary transfer
If contamination evidence is not reliable in court

32

What is the importance of reliability/safety of trace evidence?

Reputable- i.e. has there been any contamination, enough analysis
Relevant circumstances- i.e. crime in house, suspect lived in house
Funding