Prior Odds
Definition
The ratio of the probability of the prosecution hypothesis to the probability of the defence hypothesis before the forensic evidence in question is considered. Set by the fact-finder using all non-forensic case information. The forensic expert does not supply this quantity.
Related terms
- Likelihood Ratio (LR)
- The ratio of two conditional probabilities: the probability of the observed evidence given the prosecution's hypothesis (same source), divided by the probability...
- Posterior Odds
- The ratio of the probability of the prosecution hypothesis to the probability of the defence hypothesis after the forensic evidence is taken...
- Prosecutor's Fallacy
- The error of treating the RMP (or its reciprocal) as the probability that the defendant is innocent, or as the probability that...
- Evaluative Reporting
- A framework for expressing forensic conclusions in terms of the probability of the evidence given the prosecution hypothesis versus the defence hypothesis...
- Random Match Probability (RMP)
- The probability that a randomly chosen unrelated person from the relevant population would match the evidence profile by chance. A very small...
- Bayes' Theorem
- The mathematical rule that relates prior odds, the likelihood ratio, and posterior odds. In the odds form: O(Hp|E) = O(Hp) x LR....
- Defence Attorney's Fallacy
- The incorrect argument that a large global or national population means many unrelated individuals could share the profile, while ignoring the geographic...
- Defence Hypothesis (Hd)
- The proposition advanced by the defence, typically that the material came from an unknown unrelated individual or that the defendant was not...
- ENFSI DNA Working Group
- The European Network of Forensic Science Institutes DNA Working Group. Coordinates European forensic DNA standards, including the evaluative reporting guidelines adopted by...
- Hardy-Weinberg Equilibrium (HWE)
- The expected genotype frequency in a large, randomly mating population with no selection, mutation, or migration. Under HWE, the frequency of a...
- Product Rule
- The rule that, under independence, the joint probability of a multi-locus genotype equals the product of the individual locus genotype frequencies. Used...
- Prosecution Hypothesis (Hp)
- The proposition advanced by the prosecution, typically that the defendant is the source of the recovered material or was present at the...
Explained in these topics
- Bayes Theorem in Evidence EvaluationThe ratio of the probability of the prosecution hypothesis to the probability of the defence hypothesis before the forensic evidence in question is considered....
- The Likelihood Ratio: Definition and LogicThe odds that the prosecution hypothesis is true before the forensic evidence is considered. In court, prior odds reflect all evidence other than the specific...
- Prior and Posterior Odds in CourtThe ratio of the probability of the prosecution proposition (Hp) to the probability of the defence proposition (Hd) before any forensic evidence is considered....
- Allele Frequencies, Random Match Probability and the Likelihood RatioThe odds of the prosecution hypothesis relative to the defence hypothesis before the DNA evidence is considered. Combined with the LR by Bayes' theorem to yiel...