When might a statute impliedly compromise fundamental rights connected with criminal proceedings? This issue was at the heart of X7 v Australian Crime Commission  HCA 29 (26 June 2013). The Court split 3-2.
The primary question for the Court was, put broadly, whether provisions (Div 2 of Part II of the Australian Crime Commission Act 2002(C'th)) that empowered an examiner to interrogate a person, extended to questioning a person who was subject to criminal proceedings. If the provisions did have that effect, a further question of their constitutionality would arise. The majority held that the provisions did not authorise examination of a person who was subject to criminal proceedings, so that the constitutional question did not arise.
The "right to silence" – not mentioned in the relevant legislation - could be thought of as a general expression, encompassing the right of a defendant not to answer questions put by the police or other persons in authority, and the right of a defendant not to be compelled to give evidence or to assist the prosecution in discharging its onus and burden of proof. That is broadly how the minority, French CJ and Crennan J, described the defendant's rights at issue here -42], although they also mentioned – and recognised the importance of - the defendant's right to a fair trial -.
The majority, Hayne and Bell JJ jointly, with Kiefel J concurring, drew from the accusatorial nature of a criminal trial the "right to silence" and the related "privilege against self-incrimination", applicable to defendants and suspects respectively -, observing that although historically of relatively recent origin they are fundamental features of the accusatorial system of criminal justice , .
Whether a statute might, by necessary implication, compromise those features of the accusatorial process, depends on how much weight one is prepared to give them. The majority held these features are out of reach of implied compromise. They held that such an alteration would need to be made "clearly by express words or by necessary intendment" -, or – Kiefel J – "must be expressed with irresistible clearness" .
The minority said  that a compromise of one of the two aspects of the right to silence that it had identified, while the other was left intact, was a legislative balance struck here between competing public and private interests. The minority found that a legislative intent to achieve this balance could be implied from the legislative history and the context of the provision in the overall Act including its provisions that protect defendants -, -.
Recognising that a trial must be fair, and that compelling a defendant to answer questions or to give opportunities for the obtaining of derivative evidence, could not be reconciled with a fair trial , the minority pointed to the existence of powers to suppress publication of evidence, and to control who was aware of the evidence, in order to protect the fairness of a trial, calling them safeguards that are capable of preventing an unfair burden on a defendant . A trial judge's powers to prevent an abuse of process and to punish for contempt are also available to protect the fairness of proceedings , .
The majority denied that it was basing its reasoning on considerations of fairness, saying that the determinative question in this case was one of construction of the legislation . Recognising that the requirement to answer questions after being charged would fundamentally alter the accusatorial process – which includes pre-trial inquiries and investigations (Kiefel J at ) - because the defendant would have to choose at trial a course in the light of any self-incriminatory answers that may have been compelled, and that this would prejudice the conduct of the defence , it held that such a result could only be achieved by clear words or necessary intent , which were absent in the legislation here .
Looking at this case in the round, one could say that, despite the majority's disavowal of fairness as the decisive criterion, the difference between the judges illustrates inconsistent perceptions of what "a fair trial" means. For the majority a fair trial is one in which the defendant may make decisions as to the conduct of the defence without being constrained by information he was compelled to provide to officials, or by information obtained as a consequence of his being under that compulsion. The minority, referring in general terms to the judge's powers to prevent abuse of process , only say that prosecutorial reliance on compelled information would be unfair , and they do not say how a judge would determine that the prosecution had obtained "an unfair forensic advantage" .
Current exploration suggests that an element of a fair trial is impartial determination of the facts, and impartial here means both without bias and without inappropriate weight being given to any item of evidence. Constraints on the presentation of a defence, arising from compulsory interrogation, endanger the appropriateness of the weighing of the evidence by the fact-finder, and thereby endanger the fairness of the trial.
Legislated schemes for compulsory interrogation vary, as one would expect, and can include a right to claim privilege against self-incrimination coupled with a right to refuse to answer a question (subject to judicial review), as does s 138 of the Search and Surveillance Act 2012 [NZ], although in that regime failure to answer questions outside of a claim of privilege appears to be an offence: s 173. In X7 the defendant was told he had a privilege against self-incrimination but he did not have an associated right to refuse to answer questions -. He subsequently claimed privilege and refused to answer questions, which was an offence.