The first indication of a potential problem in the testing was the presence of an atypical profile of the AF, which showed evidence of a mixture of DNA (contamination). The DNA profile from the AF showed extra peaks in some loci as well as a much higher "X" allele peak relative to the "Y" allele peak at the amelogenin locus. After conducting a reanalysis by another technician with another set of positive and negative controls, analysts concluded that the only source of the mixed profile was the intentional introduction of some foreign human biological material by the AF at the point of sampling. When the AF was called back to the lab and presented with an explanation and conclusions of the findings, he admitted introducing the foreign saliva in an attempt to be excluded as the father of the child. Following this case, the sampling protocol for donors was changed. Now a staff member is always with the donor, including during the rinsing of his mouth. 2 figures, 1 table, and 4 references