A false exclusion is an inaccurate result stating that the tested father is not the biological father. Other laboratories can give false exclusions due to two main reasons: sample contamination and insufficient testing. When DNA samples are contaminated, they may result in non-matching DNA markers between the alleged father and child. In addition, insufficient testing may lead to false exclusions when there is a mutation (random genetic change) in one of the tested parties that causes a non-matching DNA marker. Extended testing is required in case of mutations, which occur in approximately 2% of the cases we test.