Forensic mathematics glossary

Not really a glossary; just a collection of miscellaneous words, not even including the most important ones (just use a searh for those). In fact the intent isn't even definitions, often just comments or links.
exclude, exclusion
frequently misused word. Consider "We excluded the man of paternity because of three exclusions." See What's wrong with the "exclusion probability" for a start.
The concept, while appealing, is dubious as well. Don't get me started.
fallacy
The terms prosecutor's fallacy and defense fallacy were, I hear, invented by UC Irvine law Prof. William Thompson.
mass identification; mass disaster identification
a DNA•VIEW speciality.
prior probability
A probability summarizing the value of the evidence prior to inclusion of (for our purposes) the DNA (i.e. scientific) evidence. The prior probability is therefore — at least in principle — a subjective assessment of anecdotal and other evidence that cannot be comfortably quantified. It's worth distinguishing several particular situations:
criminal case
The prior probability is the evidential value of evidence (such as testimony, documents, demeanor) that the DNA analyst doesn't even hear, and which in any case is the responsibility of the judge or jury to assess. Therefore it is clearly wrong for an expert witness to intrude on the prerogative of the court by making any prior probability assumption. I don't see anything wrong though with advising the court about how mathematics works, such as by a picture or a chart of examples.
(civil) paternity case
In principle the above applies to any court action. But this essay tries to take a realistic view.
disaster identification
Links: WTC and tsunami identifications
When the object of the identification is humanitarian it is typically virtually the case that decision making is deferred to the scientists. In that case, two useful concepts are:
baseline prior probability
If n people are equally missing and all bodies are indistinguishable from one another, then the prior probability for any particular identity is 1/n. This baseline prior can be a reasonable starting point in realistic scenarios as well.
requisite prior
Suppose a DNA likelihood ratio has been determined, and a posterior probability threshold for identification has been agreed. Then I define the requisite prior as that prior which is just sufficient for declaring identity.

Example: Suppose n=1000 missing, LR=80000 supporting corpse V to be missing person Jim Jones, and that the agreed policy is to declare identification when the probability is at least 99.9%. Using the baseline prior probability of 1/1000, the posterior probability only 98.8% and the threshold is not achieved. A prior of about 1/81, twelvefold larger, is the requisite prior to obtain 99.9%.

Maybe there is some quite useful non-DNA evidence supporting the ID, for example the body V shares a surgical scar approximately like Jim Jones is known to have had, and the stature is about right as well. It would be hard to estimate the exact evidential value of those coincidences, but we don't have to. It is sufficient to judge that they are worth at lease LR=12, the shortfall from the DNA evidence.

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