You are not permitted to download, save or email this image. Visit image gallery to purchase the image.
It is Dawson's second anti-doping rule violation, having been suspended for 12 months in 2014.
A Sports Tribunal ruling said Dawson had a prohibited substance, higenamine, in a sample taken from him at a National Basketball League game in May this year.
The substance came from the supplement Oxyshred, a thermogenic fat burner product used by Dawson.
He was provisionally suspended on September 4. 2017.
In a statement the tribunal said it had significant difficulties contacting Dawson who lives in Western Australia. On October 18 he formally admitted the violation and asked to be heard but failed to attend a hearing.
The tribunal cautioned Dawson that he was subject to substantial mandatory penalties, offering assistance and advice. Despite numerous efforts to engage Dawson, he did not take any action to mitigate the consequences and declined to attend a rescheduled hearing.
''He said he had outlined his circumstances and was satisfied for the matter to be dealt with in his absence,'' the tribunal said.
The presumptive period of ineligibility for the unintentional presence of a specified substance (such as higenamine) is two years. For a second anti-doping rule violation, Dawson was subject to "twice the period of ineligibility" otherwise applicable which is four years.
''Dawson exercised no caution, given the high risk associated with supplements to ensure compliance with sports anti-doping rules.
''Mr Dawson, as an experienced athlete with a previous anti-doping suspension, understood the high standards expected and the strict anti-doping obligations under the code.
''In the circumstances, the tribunal was unable to consider any elimination or reduction in the period of ineligibility.''
The four-year disqualification was backdated to July 31, 2017.
Drug Free Sport New Zealand chief executive Nick Paterson said athletes cannot afford to be complacent when using supplements.
"We can't reiterate enough how important it is for athletes to check and double check every supplement which they are thinking of taking. Manufacturers do not always list all ingredients on the label.
"And even if the ingredients are listed, it is the athletes' responsibility to check that they are permitted in sport," Paterson says.
"This is especially important with the new prohibited list coming out on 1 January 2018."