Physical Comparisons

Front 1

Quality assurance

Back 1

Peer check, training, tech & admin checks, supervisor checks, operating procedures and guidelines

Front 2

Common sense vs science

Back 2

The use of a system provides a distinction between common sense and science. It is a careful, organised, systematic way of discovering and evaluating evidence.

Front 3

Aim of comparisons

Back 3

To show a link, identification and individualisation of one physical object with another. To demonstrate a relationship.

Front 4

Class

Back 4

Class characteristics show that an object is part of a group of other objects with the same characteristics.

Front 5

Individualisation

Back 5

Identifies an individual object from within a group.

Front 6

Objectivity

Back 6

Objective information comes from the object itself. It does not involve opinion. Observations of physical proof.

Front 7

Subjectivity

Back 7

When the subject is involved other than by simple observation. It is your opinion based on your skills, experience, knowledge.

Front 8

Unique characteristics

Back 8

There are no levels of uniqueness. It is either unique or not unique.

One and only, having no like or equal.

Front 9

2 types of pattern recognition

Back 9

Pattern fit

Pattern transfer

Front 10

Pattern fit

Back 10

A physical match.

Pattern continuity: wood grain, material thread.

Fracture fit: two pieces were once one object

Pattern match: photo A matched to a scene.

Front 11

Pattern transfer

Back 11

Fingerprint, tool marks, shoe impressions. Can be 2D or 3D.

Front 12

Positive association

Back 12

Made by observing a unique pattern. Only need one unique characteristic to establish a positive match.

Front 13

Establish your experience knowledge testing to the court

Back 13

Testing done by yourself and others go towards proving your claims. Thereby supporting your assertion that uniqueness and random characteristics do not occur more than once.

Front 14

Method of comparison we use

Back 14

ACE-V

Analysis

Comparison

Evaluation

Verification

Front 15

Analysis

Back 15

Systematically detailing your observations.

Unknown (scene item, impression) is examined first then the exhibit.

Reduce the item to its properties or characteristics.

Front 16

Comparison

Back 16

Compare the scene impression with the exhibit. Measure side by side, test impressions, overlays. Looking for similarities and differences.

Front 17

Evaluation

Back 17

Have you found sufficient characteristics to preclude the possibility/probability of their having occurred by coincidence.

Can you explain the differences.

Determine your finding based on scale of conclusions.

The weight or significance of the characteristics/properties must be considered.

Front 18

Considerations when making test impressions

Back 18

Will the impressions affect other forensic evidence that may be there.

Suitable method to compare like with like. Are multiple impressions possible or would that damage the exhibit.

Duplicate the conditions of the scene.

Front 19

What can account for measurement differences

Back 19

Distortion at time of impression.

Instability of substrate.

Distortion by forces.

Different shoe.

Front 20

How are verifications of comparison work confirmed

Back 20

Peer review and blind checks.

Front 21

How do we ensure the quality of our conclusions

Back 21

QA programs, proficiency testing, sop’s and guidelines.

Front 22

Effective means of demonstrating results

Back 22

Charts and photos. Something to look at.

Front 23

How do you establish yourself as an expert.

Back 23

List your qualifications and training. List similar cases and ongoing training. Work history.

Front 24

Imaginative perception

Back 24

The mind can be tricked into believing something is there when it is not.

Avoid it by careful observation of the unknown and document your observations. Do this before looking at the known.

Front 25

Non biased approach

Back 25

Maintaining objectivity and keep opinions based on the evidence and not what another party wants.