Evaluative Interpretation of Evidence Flashcards Preview

PS712: Advanced Topics in Forensic Science > Evaluative Interpretation of Evidence > Flashcards

Flashcards in Evaluative Interpretation of Evidence Deck (5)
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1
Q

What are base rates and what is the base rate fallacy?

A

Base rates (or background rates) are the relevant frequencies of variables in the general population.

Base rate fallacy is making a probability judgement based on conditional probabilities without taking into account the effect of prior probabilities.

2
Q

What is the prosecutor’s fallacy?

A

The prosecutor’s fallacy is when the probability of innocence given the evidence is assumed to be equal to the probability that the evidence would occur if the defendant was innocent.

This is an example of transposing the conditional, and exaggerates the likelihood of a defendant’s guilt.

3
Q

Why is it beneficial to sometimes go from a source-level proposition to a activity level proposition?

A
  • When little/no expert opinion is required to evaluate evidence, it is beneficial to report at source level as it is not necessary for the court to interpret at activity level.
  • When enough information is present and the expert witness has enough expertise, it can be beneficial to interpet at activity level. This allows the court to understand more complex evidence and analysis, and can understand how the evidence may have came to be.
4
Q

What is required of the Forensic Scientist to move up the hierarchy of propositions?

A
  • For Forensic scientists to move up to activity level propositions, they must have access to circumstantial information.
  • Without such information, assumptions have to be made.
  • The forensic scientist also needs to have the relevant expertise to move up the hierarchy of propositions.
5
Q

Why should offence-level propositions never be reported by Forensic Scientists?

A
  • Offence level statements make conclusions about criminal responsibility and liability
  • Expert witnesses should not testify to propositions at offence level because:
    • They involve factual and moral judgements that forensic scientists are not jurisdictionally competent to make.
    • Was harm caused unlawfully?