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Sense-making software for crime investigation: how to combine stories and arguments? Henry Prakken...
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Transcript of Sense-making software for crime investigation: how to combine stories and arguments? Henry Prakken...
Sense-making software for crime investigation:
how to combine stories and arguments?
Henry Prakken(& Floris Bex, Susan van den Braak, Herre van Oostendorp, Bart Verheij,
Gerard Vreeswijk)New York,
January 29th, 2007
Contents A research project:
Building software that supports crime investigators
Investigate theoretical basis Stories and causality in evidential reasoning
Abduction Reasoning with testimonies:
Argumentation Combining stories and testimonies:
abduction + argumentation
Practical motivation Crime investigation often one-sided,
aiming to confirm a certain hypothesis
Dutch criminal procedure is inquisitory: Judges rely on police case files Very little investigation in court ...
So a lot can go wrong
The intended software: a sense-making system
No knowledge inside, but Supports human users in structuring and
visualising their thinking Can calculate with these structures Can link them with case files
Should be based on an account of evidentiary reasoning that is:
Prescriptive (supporting rational thinking) Natural (close to the way crime investigators think)
Anchored Narratives Theory
(Crombag, van Koppen & Wagenaar)
A rational and natural theory of evidentiary reasoning?
Recognises importance of stories (timelines!) Generalisations
Find plausible causal links within story Anchor stories in evidence
But theoretically underdeveloped Our aim: investigate theoretical foundations of
ANT Causation Testimonies
Stories involve causation Stories are (at least) a sequence of events
on a timeline Events are supposedly caused by earlier
events Physical causation Mental causation
Reasoning with causal information: Prediction: assume or observe event, predict
what will happen next Explanation: observe event, explain what could
have caused it
Example: the King case (1) Fact: King was beaten up by mr. Zomerdijk
in backyard of Zomerdijk’s house Prosecution’s story
King (a convicted thief) was up to no good King climbs into backyard of Zomerdijk family King enters bedroom King steps on toy Mr. Zomerdijk hears sound Mr. Zomerdijk goes to bedroom King closes door and runs away
Example: the King case (2) Fact: King was beaten up by mr.
Zomerdijk in backyard of Zomerdijk’s house
Defence’s story King climbs into backyard of Zomerdijk family Wind opens bedroom door Wind hits toy Mr. Zomerdijk hears sound Mr. Zomerdijk goes to bedroom Mr. Zomerdijk sees King in backyard
Representing causal knowledge
Explanation with evidential rules:
Deduction:
Explanation with causal rules:
Abduction:
Effect CauseEffect Cause
Cause EffectEffect Cause
Fire causes Smoke
Smoke
Fire
Smoke means Fire
Smoke
Fire
Abductive-logical models
Simulate abduction with deduction: Given:
causal rules T ‘explanandum’ F
Hypothesise a cause C such that T with C logically implies F (“C explains F”)
Compare all alternative explanations How much additional evidence is explained? How much additional evidence is contradicted? …
Explanations as causal networks of events
Toy makes a sound
ObservationsThe door is closed
Explanations as causal networks of events
Toy makes a sound
ObservationsThe door is closed
King enters house
King stepson toy
King closesdoor
Explanations as causal networks of events
Toy makes a sound
ObservationsThe door is closed
King enters house
King stepson toy
King closesdoor
The wind hits the toy
The wind closes
the door
The wind opens
the door
Loud bang
Explanations as causal networks of events
Toy makes a sound
ObservationsThe door is closed
King enters house
King stepson toy
King closesdoor
No loud bangwas heard
The wind hits the toy
The wind closes
the door
The wind opens
the door
Loud bang
A problem(?): testimonies must also be explained
King enters house
King stepson toy
Toy makes a sound
Observations
The door is closed
King closesdoor
Witness wants toprotect himself
Witness Z often imagines sounds
Witness Z says“I heard a sound”
Witness Z says“the door was closed”
Testimony principle is not a causal but an evidential
rule Testimony principle not represented from-
cause-to-effect:
but from-cause-to-effect:
Truth of P is the usual cause of “P”. Other causes of are exceptions.
Reasoning is then modelled as constructing and comparing (defeasible) arguments
Witness says “P” => P
P => Witness says “P”
Combining abduction and argumentation
Toy makes a sound
‘Observations’The door is closed
King enters house
King stepson toy
King closesdoor
Witness Z says“I heard a sound”
Witness Z is not sincere
Witness wants toprotect himself
Further evidence needed!
The full picture
Toy makes a sound
ObservationsThe door is closed
King enters house
King stepson toy
King closesdoor
No loud bangwas heard
The wind hits the toy
The wind closes
the door
The wind opens
the door
Loud bang
Conclusion Combining abduction for representing
stories and argumentation for reasoning about sources of evidence arguably is natural can arguably be given a sound rational
basis But all this should be further
investigated
Arguments
Assault
e1 e3
e2
hitting
p
intent
Counterarguments
Assault
e1 e3
e2
hitting
p
intent
Selfdefence
attacked
e4
e5q
Reinstatement
Assault
e1 e3
e2
hitting
p
intent
Selfdefence
attacked
e4
e5q
Not attacked
e6 e7