Combining Evidence

Details

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Version: After imprimatur
Serval ID
serval:BIB_18EB89A0CF6B
Type
PhD thesis: a PhD thesis.
Collection
Publications
Title
Combining Evidence
Author(s)
Juchli Patrick
Director(s)
Franco Taroni
Institution details
Université de Lausanne, Faculté de droit et des sciences criminelles
Address
Batochime, UNIL-Dorigny, 1015 Lausanne
ISBN
2-940098-74-3
Publication state
Accepted
Issued date
06/2016
Language
english
Number of pages
218
Abstract
The goal of the present thesis
consists of establishing the normative foundations for
reasoning about combined evidence. Unlike the inter-
pretation of single items of evidence, little is known
about inference tasks involving multiple items of evi-
dence. In forensic practice, however, experts are regu-
larly confronted with a collection of evidence rather
than isolated evidence items. This necessarily raises
the question on how to interpret evidence holistically.
The study of the relationships between the different
evidence items in a collection and between a collec-
tion and a common cause (represented as hypotheses),
is of central concern for this thesis. Such relation-
ships and causes are almost always unobservable in
judicial contexts, and therefore, inherently uncertain.
Indeed, uncertainty is a fundamental feature of rea-
soning about evidence. The framework for handling
uncertainty is defined by probability theory. Evidential
reasoning is consequentially a form of probabilistic
reasoning. The present thesis locates itself in this
probabilistic framework and puts a strong emphasis
on graphical probabilistic modeling.
The thesis is composed of four cornerstones for each
of which a paper was produced. Throughout this
thesis, the ordering of the cornerstones is thematic
and not chronological. The first paper examines the
different types of evidence and their combinations,
their generic inference structures, and the relationships
between these different inference structures. The ex-
amination establishes, thus, a probabilistic ontology
of evidence. The following study illustrates the ap-
plication of generic inference structures in two real
forensic cases. One case involves the combination of
two features of a single footwear mark. The other
involves fingermarks and a footwear mark, thus two
distinct marks. The study shows that even apparently
simple forms of combinations involve evidential sub-
tleties that require careful analysis. The third study
provides novel analysis methods for evidential phenom-
ena exclusively occurring in combined evidence. To
date, there are only a few methods for assessing the
inferential interactions between items of evidence in
a holistic setting. This study addressed this problem.
The final project consists of a complex case analysis
involving four different DNA specimens collected from
a rape case that lead to a wrongful conviction of a
young man. The model treats each specimen as a
mixture profile, and includes considerations on the
relevance of each specimen, the possible number of
contributors to each specimen, the inferential relation-
ships between the specimens, as well as between the
specimens and the hypothesis about the authorship of
the crime. As it turned out, the different specimens
were subject to strong inferential interactions − a fact
that was completely missed by the expert of the case.
This thesis shows: the problems pervading the subject
of combined evidence are not academic phantoms;
they are measurable, real, and can affect the lives of people for better or worse.
Keywords
Combining Evidence, evidence, Bayesian network, argument, inferential interaction
Create date
06/10/2016 19:43
Last modification date
20/08/2019 13:49
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