113
Classification, Identification,
and Individualization —
Inference of Source
A.
The Relationship of Evidence to Source ............................................. 114
1.
Principle, Process, or Objective .................................................... 115
2.
The Question of Source ................................................................ 116
B.
Classification — Categorization with Like Items............................... 116
1.
Class Characteristics...................................................................... 117
a.
Class Characteristics
Result from a Controlled
Generation Process................................................................. 118
b.
Items with the Same Class Characteristics May Have
Different Origins .................................................................... 119
c.
When Is Evidence Class Evidence? ....................................... 121
C.
Identification ......................................................................................... 122
D.
Individualization................................................................................... 122
1.
A Conclusion of Common Source............................................... 123
2.
Individuality and Uniqueness....................................................... 123
a.
Existent Objects Are Unique ................................................. 123
b.
The Generation of Individual Characteristics ..................... 124
i. Generation by Nature ................................................... 124
ii. Generation by Man....................................................... 125
iii. Entropy and Disorder................................................... 125
c.
The Scale of Detection Is Determined by the Scale of
Manufacture ........................................................................... 127
i. Signal vs. Noise ............................................................. 128
3.
Individualizing Characteristics ..................................................... 129
4.
Physical Evidence with Individualizing Potential ....................... 129
5.
The Conceptual Process of Individualization ............................. 130
a.
Analysis of Evidence for
Class and Individualizing
Characteristics ........................................................................ 131
i. Collection and Preservation......................................... 131
ii. Examination .................................................................. 131
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Principles and Practice of Criminalistics
E.
Inferring a Common or Different Source........................................... 137
1.
Conclusion, Inference, or Opinion of Common Source............ 137
2.
Three Inferences ............................................................................ 138
a.
The Items Originate from Different Sources ....................... 138
b.
The Items May Be Classified, but Cannot Be
Individualized Due to a Limitation
of the Evidence or
the Test .................................................................................... 139
c.
The Items Share a Unique Common Origin ....................... 139
d.
The Conclusion ...................................................................... 140
F.
Mathematical Approaches to Expressing the Strength of the
Inference ................................................................................................ 140
1.
The Necessity of Providing an Assessment of the Strength
of the Inference.............................................................................. 140
2.
Tools for Estimating the Strength of the Inference .................... 141
a.
Frequency Estimates............................................................... 142
b.
Likelihood Ratios ................................................................... 142
i. Likelihood Ratios in Bayes’ Theorem.......................... 144
3.
Classification.................................................................................. 145
a.
Hypothesis Testing vs. Bayes’ Theorem — Which One?..... 147
4.
Individualization ........................................................................... 147
a.
Individualization and Opinion — A Special Case .............. 148
G.
Summary ............................................................................................... 150
References ...................................................................................................... 151
The chemical composition between the two was found to be …
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