This is in regards to claims that DNA evidence could be planted or falsified.
Planting evidence in one crime scene in this day and age is hard, It can be done and does continue to happen but planting evidence across multiple crime scenes makes things even harder. When collecting or accessing evidence there is a chain of command. A police officer, detective or forensic expert must sign for the evidence on both check out and check in of storage. If someone were to plant DNA in the evidence files for the Huntingdale attack, Karakatta rape kit and Ciara Glennon murder there would be a paper trail as clear as day. It is not an impossible probability of this happening but the chances are that slim that I would personally consider it to be non existent. Evidence is preserved in the condition they were received in. they are kept in a security sealed evidence bag that cannot be interfered with. Outside of LE experts might have access to the evidence but the require an expert certificate and also must follow the same procedures put in place for LE. Planting evidence is most likely to occur at the time of evidence collection (accounting for 89.2% of proven evidence tampering cases) I just find it inconceivable that police would have planted DNA evidence for one Bradley Robert Edwards at the time of collection with a cunning master plan of making the link some 20 years later.
DNA evidence alone will not convict criminals so even if the jury is presented with the slightest hint of doubt police will introduce evidence of the crime, character, reputation or conduct of the defendant, or evidence of a tendency the defendant has or had in order to make their case. The DNA evidence, considered with all the other evidence in the case, is likely to show there is no other reasonable explanation other than the defendant's guilt but it will not be the sole evidence for making the case against Bradley Edwards.