Forensic science, criminalistics, CAI

Question 1

What are criminal investigations?

Answer 1

• continual process
• begins with crime and crime scene
• involves suspects

Question 2

What are the 2 stages of criminal investigations?

Answer 2

1. Investigative
2. Evaluative

Question 3

What is the Investigative stage?

Answer 3

To find
To propose explanations about what’s happened and suggest possible perpetrators. Who? What? Why? When? How?

Question 4

What is the evaluative stage?

Answer 4

To prove
To assess if the suspect is the person who committed the crime.
Did the accused do it?

Question 5

Where does forensic science fit into criminal investigations?

Answer 5

• policing - making connections
• investigation - crime scene, suspect
• trial - evidence assessment

Question 6

What is forensic science?

Answer 6

Application of science during criminal investigations. To collect relevant and helpful info from physical traces to answer questions of interests.

forensics = before the forum (court)

Question 7

What are the challenges with forensics?

Answer 7

1 - unique issues
transfer/persistence of evidence

2 - requires a detailed understanding of unique issues for the interpretation of findings

3 - requires comprehendible/accurate communication of findings to assist courts

Requires logical framework to operate criminalistics.

Question 8

What is criminalistics?

Answer 8

Application of science for the analysis/examination of physical evidence, interpretation, and presentation in court.
- general context -> legal framework, evidence admissibility
- fundamental forensic concepts
- specific ways of thinking -> evidence interpretation
- general analytical approaches

Question 9

What is the unified forensic paradigm?

Answer 9

Logical framework of forensic progression surrounding a crime.

Question 10

What are the principles of this paradigm?

Answer 10

Principles - evidence generation
1. Divisibility of matter
2. Principle of exchange

Mechanisms through which physical evidence is created independent of human intervention.

Question 11

What are the processes of this paradigm?

Answer 11

Processes - forensic practice
1. Process of identification
2. Process of individualisation
3. Process of association

Decisions made during case investigation. They are dependent on human intervention. If a crime is never identified/evidence isn’t recovered - these processes don’t start.

4. Process of reconstruction

Question 12

What is the focal point of the model?

Answer 12

The crime -> suspect, witness, victim, scene

Generation of evidence - practice of forensic science

Question 13

How is crime the focal point of forensics?

Answer 13

1 - starting point
When physical traces are created and where forensic science begins

2 - final objective
Crime reconstruction is the event of interest of forensic exploitation of physical evidence

Question 14

What are the key crime characteristics?

Answer 14

• unique circumstances
• interacts with different entities -> scene, victim, suspect, witnesses
• is it premeditated?
• occurred in the past

Question 15

What does the unified model do?

Answer 15

Helps reconstruct events and provides info on what’s happened -> crime reconstruction. Can’t be 100% sure of what’s happened as we weren’t there so have to use knowledge and evidence.

Question 16

What is concept 1?

Answer 16

Divisbility of matter
Inman/Rubin 2002

Question 17

What is the Divisibility of matter concept?

Answer 17

1. Matter divides into smaller components when sufficient force is applied
2. Parts will require new characteristics created by divisibility
3. Retains physicochemical properties of the original

Question 18

What are the consequences of concept 1?

Answer 18

• some characteristics retained by the trace are common to the original and other objects
• some characteristics retained by the trace are unique to the original or division process -> such as unique edge pattern
• some characteristics are lost/changed complicating it

Relates to the processes of individualization/identification

Question 19

What is concept 2?

Answer 19

Principle of exchange -> every contact leaves a trace
Edmund Locard 1963

Question 20

What is the principle of exchange?

Answer 20

Locard’s exchange principle:
‘It’s impossible for a criminal to act without leaving traces of presence, especially considering crime intensity. Through inverse actions, they will collect on his/hers body/clothes showing traces of presence and actions.

Question 21

What are the challenges of concept 2?

Answer 21

• traces are left after each interaction between different entities
• some traces come directly from the offender or left at the crime scene, or on the victim
• some traces are left by the scene, victim witnesses, and picked up by the offender

Question 22

What is concept 3?

Answer 22

Process of identification

Question 23

What is the process of identification?

Answer 23

Direct consequence from, divisibility of matter.
- identification is 1st step
- common characteristics allow identification

Question 24

What is an example of the process of identification?

Answer 24

Toxicology/drug analysis
Simple possession of classified drugs is illegal and CJS may not be concerned about the origin of it.

Question 25

What are the consequences of concept 3?

Answer 25

Some characteristics are retained by traces and are common to both original and similar items.

Question 26

What is concept 4?

Answer 26

Process of individualization Kirk 1963

Question 27

What is the process of individualization?

Answer 27

'Process of narrowing down a class to one member -> determines specific sources of a piece of evidence' - Carried out by comparison analysis with question and reference samples. - Direct consequence from divisibility of matter - unique characteristics allow individualization of specific sources if the sample is analyzed

Question 28

What are the consequences of concept 4?

Answer 28

Some characteristics are retained by traces unique to the original or division process.

Question 29

How is identification/classification possible?

Answer 29

Possible due to class characteristics that are common to several different sources (objects of the same model) -> general population

Question 30

How is individualization possible?

Answer 30

Possible due to individual characteristics specific to a single source -> source of trace

Question 31

What is concept 5?

Answer 31

Process of association - Direct consequence of exchange Osterburg 1968

Question 32

What is the process of association?

Answer 32

'Process of linking a person with a crime scene - inference of contact between the source of evidence and recipient surface by transfer detection.'

Question 33

How does the process of association occur?

Answer 33

Traces left after each interaction between different entities involved in crime depend on: source (recipient surfaces), activities, and external factors. Require knowledge of evidence gathered during the process of individualization.

Question 34

What is concept 6?

Answer 34

Process of reconstruction DeForest et al 1983

Question 35

What is the process of reconstruction?

Answer 35

'Process of understanding the sequence of past events, i.e. ordering associations in space/time'

Question 36

What is reconstruction?

Answer 36

Ordering events in space/time based on physical evidence to answer where, how, and when. Contrast to individualization which attempts to reply to the questions of who and what.

Question 37

What is evidence interpretation?

Answer 37

Forensic scientists report their findings accurately and don't over/under state evidential value/mislead courts.

Question 38

What's the hierarchy of propositions?

Answer 38

L3 - offence L2 - activity L1 - source Opposing proposition statement presented by: - prosecution (Hp) - defense (Hd) 1. Different evidence types provide different info 2. Govern questions answered by evidence/findings

Question 39

What are the 2 features every physical trace is characterized by?

Answer 39

1. source level 2. activity level

Question 40

What is the source level?

Answer 40

Intrinsic (IC) characteristics are inherent to every single element of the trace. Depends on the original material: - composition - physical properties - shape of glass, fibres, particles, etc

Question 41

What is the activity level?

Answer 41

Extrinsic (EC) characteristics inherent to traces when taken as a group. Depend on activity type which left the traces: - number/amount of particles, etc - spatial distribution - position

Question 42

Example of source and activity level - fibers recovered from front passenger car seat

Answer 42

Intrinsic (IC) - composition, physical properties, shape Depend on the source - physiochemical properties Extrinsic (EC) - number/amount, pattern/ position Depend on activity - how the trace is transferred

Question 43

Example of source and activity level - glass fragments

Answer 43

IC - info - composition and RI EC - info - number of fragments/position

Question 44

What do intrinsic and extrinsic characteristics do?

Answer 44

IC - discriminate between different sources which could have left traces EC -discriminative between different activities which could've left traces Links suspect to crime scene - association Every examination protocol should determine the IC and EC

Question 45

What are the forensic considerations to take towards a case?

Answer 45

Can't analyze every item/trace found at the scene due to: - time (delays investigation) - money - evidence interpretation A selection procedure is needed!

Question 46

What is the selection model called?

Answer 46

Reasoning model - Case Assessment Interpretation (CAI)

Question 47

What does the reasoning model do?

Answer 47

1. Provides a rational, step-based approach 2. Helps decision making - identifying the most useful traces 3. minimises cost/time 4. maximises efficiency

Question 48

What is the CAI?

Answer 48

1 - Customer requirement -> Customer needs 2 - Case pre-assessment -> Examination strategy and evidence prioritization 3 - Service delivery -> statement

Question 49

What do you need to do during the customer requirement stage?

Answer 49

- acquire knowledge about case context - clarify needs of investigation (public) or customer (private)

Question 50

What do you need to do during the case pre-assessment stage?

Answer 50

- define questions that need to be answered - determine exam strategy - identify relevant items/traces - assess their usefulness in response to the questions - priority and plan

Question 51

What do you need to do during the service delivery stage?

Answer 51

- analyze items/traces - interpret findings - produce a statement

Question 52

What information does the submission form contain?

Answer 52

- case reference details - crime - case circumstances - understanding - suspects - points to prove - what questions need to be answered? - loss of exhibits