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Gianluca Baio Evidence Project, UCL

Comments on: “The impact of discredited evidence” by David Lagnado & Nigel Harvey. Gianluca Baio Evidence Project, UCL. EVIDENCE 2 Neighbour 2 says S was outside house on night of crime.

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Gianluca Baio Evidence Project, UCL

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  1. Comments on: “The impact of discredited evidence” by David Lagnado & Nigel Harvey Gianluca BaioEvidence Project, UCL

  2. EVIDENCE 2 Neighbour 2 says S was outside house on night of crime Scenario: House burglary, local suspect S apprehended (1) HYPOTHESIS: Suspect S did it EVIDENCE 1 Neighbour 1 says that S often loiters in area ? Neighbour 2 is lying because he dislikes S (Alleged) direct influence of knowing that Evidence 2 is discredited on Evidence 1

  3. Scenario: House burglary, local suspect S apprehended (2) HYPOTHESIS: Suspect S did it EVIDENCE 1 Neighbour 1 says that S often loiters in area EVIDENCE 2 Neighbour 2 says S was outside house on night of crime Is Neighbour 1 lying too? Neighbour 2 is lying because he dislikes S When Evidence 1 & Evidence 2 are observed, knowing that Evidence 2 is discredited influences indirectly the credibility of Evidence 1

  4. Scenario: House burglary, local suspect S apprehended (3) Representation in terms of a BN consistent with the fact that ‘corroborating evidence’ is integrated (link between Reliability Evidence 1 & Reliability Evidence 2, when Evidence 1 & Evidence 2 are observed Does not accommodate differences related to temporal ordering

  5. Intervention model (agent-based causality) HYPOTHESIS: Suspect S did it EVIDENCE 1 Neighbour 1 says that S often loiters in area EVIDENCE 2 Neighbour 2 says S was outside house on night of crime Is Neighbour 1 lying too? Neighbour 2 is lying because he dislikes S If Evidence 2 is known to be “manipulated” (intervened on), the link between Hypothesis S & Evidence 2 is removed. Evidence 2 becomes essentially irrelevant

  6. Intervention model (agent-based causality) (2) • 1. Observe Evidence 1 • Update Hypothesis S & Reliability of Evidence 1 • 2a. Observe Evidence 2 • Update Hypothesis S, Reliability of Evidence 1 & Reliability of Evidence 2 • 2b. Observe Manipulation (discredit Evidence 2) • Update only Hypothesis S & Reliability of Evidence 1

  7. Intervention model (agent-based causality) (3) Including a Control Evidence (i.e. check an alibi) could be a good alternative to qualify the extent to which Evidence 2 is discredited. Probably, the Hypothesis S & Reliability of Evidence 1 would be affected in a more appropriate way

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