4104FSBMOL - Lecture 1b - Trace Evidence Analysis & Microscopy.

Question 1

What is the DEFINITION of Trace Evidence?

Answer 1

Microscopic quantities of material that are of probative value in a forensic investigation.

(Almost anything can be encountered as trace evidence)

Question 2

What are the different Types of Trace Evidence?

Answer 2

• Biological (Human).
• Physical (incl. biological [non-human]).
• Particles, Substances, Marks/ Impressions.
• Natural vs. Manufactured Materials.

Question 3

What are the 6 Steps in Trace Evidence processing?

Answer 3

1. Transfer.
2. Persistance.
3. Collection.
4. Analysis.
5. Interpretation.
6. Presentation.

Question 4

What are Evidence Dynamics?

Answer 4

“any influence that adds, changes, relocates, obscures, contaminates, or obliterates physical trace evidence, regardless of intent”.

Question 5

What is Locard’s Exchange Principle?

Answer 5

“Every Contact Leaves a Trace.”

Question 6

What are the different Modes of Transfer?

Answer 6

• One-way.
• Two-way.
• Direct vs. Indirect.
• Secondary Transfers.

Question 7

What is a ‘One-way’ transfer?

Give an Example.

Answer 7

Evidence is left on one thing.

E.g. Fingerprints are Left on a gun/ GSR left on someone.

Question 8

What is a ‘Two-way’ transfer?

Give an Example.

Answer 8

Something which can pick up and leave evidence.

E.g. Broken glass can pick up fibres/ remove them from someones clothing.

Question 9

What is a ‘Direct’ transfer?

Give an Example.

Answer 9

Something/ someone is in contact with something.

E.g. A shoe in soil.

Question 10

What is a ‘Indirect’ transfer?

Give an example.

Answer 10

Something/ someone transfers evidence without contact.

E.g. Someone coughing on someone else.

Question 11

What are ‘Secondary Transfers’?

Give an example.

Answer 11

Evidence is Left and then transferred somewhere else.

E.g. someone drinking out of a bottle and then another person after - transferral of saliva.

Question 12

What is an example of a CASE STUDY for Hairs and Fibres?

Answer 12

The Soham Murders 2002.

Question 13

What happened in the Soham Murders 2002?

Answer 13

• 40,000 hairs and fibres were examined.’
• 2-way transfer of 154 fibres.
• Material found in suspects hoover linked to the soil where the bodies were buried.

Question 14

How is there ‘Variation in Transfer’ in Clothing?

Answer 14

• Varied Composition, Texture.
• Fibre Shedding.
• Wool retains material better etc.

Question 15

How is there ‘Variation in Transfer’ in Weather?

Answer 15

• Conditions affect the transfer of environmenal trace evidence (location of source).
• Influences deposition of other evidence at the scene.

Question 16

How is there ‘Variation in Transfer’ in Trace Characteristics?

Answer 16

• Particle Size/ Shape.
• Glass: fragments (mm) or particles (μm).
• Pollen - different sizes and textures.

Question 17

How ‘Frequent’ is Pollen Evidence?

Answer 17

• Abundant in the environment.
• Direct/ Indirect Transfer.
• Present in Hair, on shoes and Clothing.

Question 18

How ‘Frequent’ is Glass Evidence?

Answer 18

• Rare among the General Public.

CASE STUDY: Jackson et al (2013)
- 6 fragments - 232 memebers of the public.
- 138 fragments - 15 people in industry.

Question 19

How does Wear affect ‘Trace Persistance’ of Evidence?

Answer 19

• Loss of evidence over time - Decay Curve.
• Fibre persists on certain items of clothing.

Question 20

How does Offender Activity affect ‘Trace Persistance’ of Evidence?

Answer 20

• Post-crime activity can lead to a loss of trace evidence - e.g. bystanders, police, CSI’s.
• Washing, Burning, Cleaning, Vacuuming leads to a loss of evidence.
• Packaging Evidence - loss/ redistribution of evidence.

Case Study: soil extracted from washing machine as someone attempted to get soil out of clothes.

Question 21

What CASE STUDY links to Trace Evidence?

Answer 21

Terrorism Trial (1998).

Question 22

What happened in the Terrorism Trial (1998) Case?

Answer 22

• Car set on fire - physical evidence lost.
• Soil recovered from tires - compared.
• As Soil is persistent the evidence is valid.

Question 23

What Techniques can be used to Collect Trace Evidence?

Answer 23

• Picking, Scraping, Brishing, Combing.
• Tape Lifts.
• Vacuum.
• Swabs.

Question 24

How is Trace Evidence Analysed?

Answer 24

• Via Class Characteristics (colour, shape, refractive index).
• Absolute Identification not always possible so instead need to EXCLUDE evidence.
• SEM-EDX.

Question 25

What ways can you Classify Trace Evidence?

Answer 25

* Shape. * Physical/ Chemical Properties. * Melting/ Boiling Point. * Refractive Index (RI). * Density. * Molecular Mass. * Colour. * Absorption/ Emission Spectra (IR, Vis, UV).

Question 26

What 2 different Techniques are used for Trace Evidence? | (general)

Answer 26

* **Destructive** - e.g. Chromatography/ Mass Spectroscopy. * **Non-Destructive** - e.g. Microscopy.

Question 27

What is fundamentally the most important tool for trace evidence examiners?

Answer 27

Microscope.

Question 28

What are the Different **Types of Microscope**?

Answer 28

* **Stereo** Microscope. * **Compound** Microscope. * **Scanning Electron** Microscope (SEM).

Question 29

What **Magnification** can a **Stereo Microscope** view?

Answer 29

**30x** Mag.

Question 30

What **Magnification** can a **Compound Microscope** view?

Answer 30

**100-1000x** Mag.

Question 31

What **Magnification** can a **Scanning Electron Microscope** view?

Answer 31

**10-500,000x** Mag.

Question 32

What is a **Stereo Microscope** used for?

Answer 32

* Segregating Evidence from other material. * More in-depth analysis. * Isolation of individual particles.

Question 33

How is a **Compound Microscope** used?

Answer 33

* Transmitted Light. * Light from base goes through condenser to specimen. * Light goes through objectibe and ocular lens'.

Question 34

How is a **Scanning Electron Microscope** used?

Answer 34

* Gold Coated samples. * Scans surface with a high-energy electron beam. * Secondary Electrons detected. * Combine with chemical analysis (e.g. XRD, EDX, EDS).

Question 35

How do you interpret Trace Evidence?

Answer 35

* Comparison & **Exclusion** of samples. * Refer to Databases, Scientific Reports, Scientific Surveys. * Examiner Experience.

Question 36

Where is **Paint** Trace Evidence found?

Answer 36

* Burglaries. * Vandalism. * Assaults. * Vehicular Crimes.

Question 37

What types of **Paint Trace Evidence** can be found?

Answer 37

* Fragments. * Chips. * Particles.

Question 38

What **Analytical Tools** are used for **Paint Trace Evidence** Analysis?

Answer 38

* Stereo-microscopy. * Solvent Tests. * IR Spectroscopy. * SEM-EDX, XRD. * Pyrolysis gas chromatography.

Question 39

What CASE STUDY involves **Paint Trace Evidence**?

Answer 39

Green River Killer (1982-1995).

Question 40

What happened in the **Green River Killer (1982-1995)** case?

Answer 40

* Suspected of Murdering 104 women. * DNA identification in 2001. * Paint Spheres (Spray Paint) was found linking all the women to him.

Question 41

Where is **Glass** Trace Evidence found?

Answer 41

* Burglaries. * Vandalism. * Assaults. * Vehicaular Crimes.

Question 42

What is **Glass** made up of?

Answer 42

* Sand. * Sodium Carbonates. * Calcium Oxides. * Impurities.

Question 43

What types of **Glass Trace Evidence** can be found?

Answer 43

From Shards of Glass to Microscopic Particles.

Question 44

What **Classification** is used for **Glass Trace Evidence** Analysis?

Answer 44

* Pattern Matching (physical fit). * Density (floatation method). * Refractive Index (RI).

Question 45

How is the **Refractive Index** of **Glass Trace Evidence** Tested?

Answer 45

* How light bends as it passes through material. * Oil Immersion Method (Becke-line). * Temperature varied until a line disappears.

Question 46

What CASE STUDY involves **Glass Trace Evidence**?

Answer 46

Hit and Run (2010).

Question 47

What happened in the **Hit and Run (2010)** case?

Answer 47

* Glass recovered from victims clothing + suspects house. * 2-way trasfer of glass and foam on footwear.

Question 48

What is **Fibre Trace Evidence** used for?

Answer 48

* Natural & Synthetic Fibres. * Indicate direct contact between persons and/or scenes. * Prevalent in the environment.

Question 49

How is **Fibre** Trace Evidence **Classified**?

Answer 49

* Nature of the Fibre. * Colour. * Pigment Distribution. * Geometry. * Surface Characteristics. * Additives.

Question 50

What **Techniques** are used for **Fibre Trace Evidence** Analysis?

Answer 50

* Microscopy. * Micro-spectrometry (MSP). * Fourier Transform Infrared Spectroscopy (FTIR). * Chemcial Composition (e.g. GC/MS).

Question 51

What 2 CASE STUDIES involved **Fibre Trace Evidence**?

Answer 51

* Murder and Kidnapping of **Sarah Payne** (2000). * **Stephen Lawrence** racial motivated attack (1993).

Question 52

How does **Fibre Trace Evidence** link to the **Murder and Kidnapping of Sarah Payne (2000)** case?

Answer 52

* Fibres from suspect present in victims hair and on victims shoes. * Single hair on suspects jumper - victims.

Question 53

How does **Fibre Trace Evidence** link to the **Stephen Lawrence (1993)** case?

Answer 53

* 5 suspects identified in 1996. * New forensic evidence (Hair + Fibres) investigated in case review in 2007. * 2 finally convicted of murder in 2012.

Question 54

What is the most frequent type of Environmental Evidence transferred?

Answer 54

Soil + (plants).

Question 55

What CASE STUDY links to **Soil** as Environmental Evidence?

Answer 55

Murder in 1996.

Question 56

What CASE STUDY uses **Pollen** as Environmental Evidence?

Answer 56

Leanne Tiernan Murder (2001).

Question 57

What CASE STUDY uses **Diatoms** as Environmental Evidence?

Answer 57

Natalie Williams Murder (2002).

Question 58

Where are **Diatoms** found?

Answer 58

In Water.

Question 59

What types of crime are **Diatoms** most likely found?

Answer 59

Drownings.

Question 60

What it is more important to do than try to Match Trace Evidence?

Answer 60

**Exclude** Evidence.