Symbolic Kinship Program

Abstract

This paper discusses a computerized algorithm to derive the formula for the likelihood ratio for a kinship problem with any arbitrarily defined relationships based on genetic evidence. The ordinary paternity case with the familiar likelihood formula 1/2q is the commonest example. More generally, any miscellaneous collection of people can be genetically tested to help settle some argument about how they are related, what one might call a “kinship” case. Examples that geneticists and DNA identification laboratories run into include sibship, incest, twin, inheritance, motherless, and corpse identification cases. The strength of the genetic evidence is always described by a likelihood ratio. The general method is described by which the computer program finds the formulas appropriate to these various situations. The benefits and the interest of the program are discussed using many examples, including analyses that have previously been published, some practical problems, and simple and useful rules for dealing with scenarios in which ancestral or fraternal types substitute for those of the alleged father.