Posterior odds
Definition
The ratio of the probability of the prosecution hypothesis to the probability of the defence hypothesis after the forensic evidence is taken into account. Calculated as prior odds multiplied by the likelihood ratio. This is the updated belief state, which the fact-finder uses alongside all other case evidence.
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...
- Prior odds
- The ratio of the probability of the prosecution hypothesis to the probability of the defence hypothesis before the forensic evidence in question...
- Evaluative reporting
- A framework for expressing forensic conclusions in terms of the probability of the evidence given the prosecution hypothesis versus the defence hypothesis...
- 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...
- 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 hypothesis (Hd)
- The proposition advanced by the defence, typically that the material came from an unknown unrelated individual or that the defendant was not...
- 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...
- 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...
- Transposition fallacy
- The error of treating the probability of the evidence given a hypothesis as though it were the probability of the hypothesis given...
Explained in these topics
- Bayes Theorem in Evidence EvaluationThe ratio of the probability of the prosecution hypothesis to the probability of the defence hypothesis after the forensic evidence is taken into account. Calc...
- The Likelihood Ratio: Definition and LogicThe odds that the prosecution hypothesis is true after incorporating the forensic evidence. By Bayes' theorem, posterior odds = prior odds multiplied by the LR.
- Prior and Posterior Odds in CourtThe updated ratio after the likelihood ratio has been applied: posterior odds = prior odds x LR. The fact-finder uses posterior odds (combined with all other e...