Methods of parentage testing

Blood group testing

35.16 Traditionally, parentage testing was conducted by blood group (serological) analysis. Blood group analysis involves the use of scientific principles regarding the inheritance of blood types to establish whether a person is excluded as the parent of a child, or whether a person may be the parent of a child—it cannot establish with certainty that a person is the parent of the child.^[4]

DNA testing

35.17 DNA parentage testing has developed since the mid-1980s and is generally considered to be a more reliable form of testing than blood group testing. As with serological testing, it cannot definitively prove that a person is the biological parent of a child but instead produces a probability of parentage.^[5] DNA parentage testing is usually conducted using the polymerase chain reaction method (see Chapter 10).

35.18 DNA parentage testing usually involves determining whether the putative parent has a series of DNA markers identified as having been inherited by the child. For example, in paternity testing, it is assumed that the mother is the biological mother of the child, and that half of the child’s DNA has been inherited from her. The analyst then identifies a series of DNA markers that must have been inherited from the biological father. If the putative father does not carry all of the required DNA markers, he can be definitively excluded as the biological father of the child. If the putative father does carry all of these paternal markers, either:

• he is the biological father of the child; or

• he is not the biological father but carries the genes by co-incidence.^[6]

35.19 As it is not possible to prove paternity absolutely, the scientist then estimates the probability that the putative father is the biological father of the child.