This is a question that we are often asked at Freedman & Gopalan Solicitors, and the position is relatively clear in New South Wales.
If the DNA test or paternity test requires the taking of a sample from the body of an adult son, for example, a buccal swab, hair, blood, or nail test, without the knowledge and consent of the adult son, it will almost certainly give rise to civil liability for the person taking the sample. At common law, any physical interference with a person without their consent will amount to a battery or trespass to the person.
However, if the adult son is competent, the parent will have no authority to consent on behalf of the adult son. Adults are presumed competent, and incompetence is specific to the particular decision and cannot be presumed on the basis of a diagnosis, for example, autism. This is the position under the Guardianship Act 1987 NSW and NSW Capacity Guidelines.
In practice, reputable legal providers of legal DNA tests tend to require the participation, consent, and identification verification of the tested individual and therefore cannot be relied upon in covert practices for legal purposes.
Some individuals ask if the DNA sample can be collected from an item that is discarded, like a cup or tissue. While this prevents bodily interference, there are still some legal implications that must be faced. The collection of this information is covered under the Health Records and Information Privacy Act 2002 (NSW), where the regulation of the collection, use, and disclosure of the information is governed by testing providers. There are also “discarded item” questions that are highly dependent on the facts of the specific case, which makes reliability low.
Testing companies commonly cited as service providers include EasyDNA Australia, DNA Solutions Australia, and DNA Labs Australia, which are all operating within the aforementioned legal and regulatory guidelines.
The bottom line:
With respect to NSW law, a DNA test for an adult son without his consent, especially where bodily materials are used, is not only legally risky but will yield no legally admissible or reliable result.