It's not really the police to blame here but the judicial system and by extension the Australian people.
It's the police prosecution's job to prosecute - to present the case against an individual charged with a crime. It's the court's job to determine what, of the evidence provided, is credible and whether the weight of evidence is sufficient to convict. Er go, a judge allowed a jury to be convinced of this evidence.
Assylum seekers haven't really been making headlines in Australia in the last decade or so as a result of a raft of aggressive policies that Australians have supported all the way along. Lets not forget the fever pitch of the successful "stop the boats" liberal campaign in 2013, that Australia showed dramatic support for.