RELATIVES

• Jurisdiction: Australia

RELATIVES

[80A.2900] Overview

Relatives are more likely to share alleles than unrelated people. Therefore, a close relative of the suspect is more likely than a "random man" to have the same profile as the suspect. A possible criticism of the so-called "random match" probability is that it overestimates the strength of the evidence in a case where a relative (eg, a brother) of the suspect cannot be excluded as the actual offender: see Evett and Weir (1998), p 117. The "Brother" defence is only possible where the brother has not been tested, and the probability must be estimated that the brother (or other suggested relative) has the same profile as the suspect.

Two relatives may share some alleles because the alleles are inherited from a common ancestor (they are identical by descent). Alternatively, they may have matching alleles by chance, even if the alleles cannot be traced back to a common ancestor. Balding and Nichols (1994) and Evett and Weir (1998) derived formulae for the probability that pairs of relatives share 0, 1 or 2 alleles that are identical by descent. Balding and Nichols called these...