I agree the process wasnt appropriate, but that shouldnt mean the information collected isnt appropriate. If ASADA did start again, and they players told the truth like they should, why should their testimonies be any different?
For me, the key question is whether the way the information was collected impacts on its trustworthiness.
In other words, as long as the trustworthiness / integrity / believability of the information collected isn't compromised by
how it was collected, I don't have a problem with it being used. If laws were broken as part of the collection process, then appropriate punishments / discipline should also be handed out.
So if you put a suspect in a cell and beat them to extract a confession, this seriously compromises the trustworthiness of the confession - the beating makes the confession more likely to be fake and / or the suspect telling the police just what they want to hear - which should render it legally unusable / inadmissible.
On the other hand, if you tap a phone line, but don't quite complete the paperwork 100% correctly, there may be no impact to the trustworthiness of the information collected, but there may separately be administrative sanctions against the people involved for not complying with the required process.
The issues of whether ASADA 'fairly' use the information collected, and whether their role is to properly investigate or simply to try to maximise the chances of getting a conviction, are separate issuesm that would still be relevant even if the information were collected without coercion.