Although an appeal from the Northern Territory, the High Court’s decision in Nguyen v The Queen impacts evidence law in all Australian jurisdictions.
Sometimes, in a criminal trial, the prosecution will bear a duty to adduce material evidence, regardless of whether it favours the prosecution case or not. This is to be distinguished from the prosecutorial obligation of disclosure. Disclosure is where the prosecution provides all relevant material to the defence, which may or may not be tendered into evidence during the trial. But, in some circumstances, the prosecution might also be obliged to adduce the evidence at trial, such as by calling witnesses relevant to the charge. This can be advantageous to the defence.1 The circumstances under which the prosecution is obliged to adduce evidence in a criminal trial was considered by the High Court in Nguyen v The Queen.
In this appeal the High Court unanimously affirmed the fundamental prosecutorial duty. All of the Justices held that, in the circumstances of the case, the prosecution was obliged to tender an electronic record of interview (EROI) of the police with the appellant at his trial. The Justices reasoned differently as to the circumstances in which the prosecution would be bound to adduce evidence.
The appellant was charged on indictment of one count of unlawfully causing serious harm to another and one count of assault aggravated by the use of an offensive weapon.
The procedural history is notable in two respects. First, it commenced as a referral on a question of law. In many jurisdictions, a trial judge has the power to refer a question of law to an appeal court.2 In Western Australia, the procedure is available, but sparingly exercised.
Secondly, this was the appellant’s second trial. The first trial resulted in a hung jury (a type of mistrial where the jury is unable to reach agreement as to whether the accused is guilty or not guilty).
During the appellant’s first trial, the prosecutor played a video record of a ‘mixed interview’ to the jury. The appellant made mixed statements: comprising inculpatory statements (which tended to incriminate him) and exculpatory statements (which tended to introduce doubt as to his guilt). Although hearsay,3 the inculpatory statements were admissible as admissions against interest, and the exculpatory statements were admissible under the ‘mixed statement’ exception to the hearsay rule.
The contest arose as a result of the prosecutor’s decision, during the second trial, not to play the accused’s EROI to the jury. The prosecutor admitted this was a ‘tactical decision’.4 The Full Court of the Supreme Court of the Northern Territory (Kelly, Blokland and Barr JJ) held that the prosecutor was under no duty to tender the EROI.5
Decision of the High Court:
The majority of the High Court (Kiefel CJ, Bell, Gageler, Keane and Gordon JJ) affirmed the prosecutorial obligation in terms of adducing all ‘available, cogent and admissible evidence’:
What was said in [R v Soma] should be understood not just as a caution to prosecutors about being selective but rather as a reminder about the prosecutorial obligation to present all available, cogent and admissible evidence. Cases involving the omission of a vital witness may provide somewhat more stark examples of a failure properly to exercise that discretion than a mixed statement given by an accused in a police interview, but the latter may have just as important an impact on the outcome of the trial and the need for a new one.at 
Their Honours noted that there may be cases where it was justified for the prosecution to not adduce evidence.
There may be circumstances where it would be unfair to an accused to tender a record of interview, for example where the accused has refused to comment. In such a circumstance the omission of that evidence is justified. But where an accused provides both inculpatory and exculpatory statements to investigating police officers, it is to be expected that the prosecutor will tender that evidence in the Crown case, unless there is good reason not to do so, if the prosecutorial duty is to be met.at 
Their Honours accordingly held that the prosecutorial duty required the prosecution to adduce the EROI.
While agreeing with the outcome, Nettle and Edelman JJ both wrote individual concurring judgments, differing as to their reasoning. Justice Nettle expressed concern at the development of a general principle given that the decision to adduce evidence is a highly fact-sensitive and context-driven exercise. His Honour said:
… I am not persuaded, that the Crown’s obligation of fairness ordinarily extends to the presentation to the jury of “all available, cogent and admissible evidence” … [T]here may well be unexceptional cases in which a prosecutor would be perfectly entitled to choose not to tender available, cogent and admissible evidence without risk of unfairness to the accused.
Of course, each case depends on its own facts and circumstances, and, in the end, the question of whether a prosecutor’s decision not to tender some piece of evidence is productive of a substantial miscarriage of justice can only be judged in hindsight on appeal against conviction. But, if for no other reason than that, I am not willing to predicate as a proposition of apparently general application that the Crown’s obligation to put its case fully and fairly includes a prima facie duty to adduce all “cogent” and admissible evidence available to the Crown.at – (citations omitted)
Justice Edelman demonstrated apparent concern over Nguyen‘s procedural path to the High Court, being an appeal from a referral of a question of law. His Honour considered it was difficult to discern, in advance, whether the failure to adduce the evidence would give rise to a miscarriage of justice.
A so-called “obligation” to tender a video record of interview, like a so-called “obligation” to call a witness, is not a free-standing obligation at all. It is an aspect of the prosecutor’s duty of fairness. The content of the prosecutor’s duty of fairness depends upon all the circumstances at trial. It can never be said with certainty prior to the conclusion of the prosecution case that a prosecutor’s duty of fairness would necessarily require a witness to be called or a video record of interview to be tendered. An initial impression that fairness would require a witness to be called or a video record of interview to be tendered might be affected by later circumstances, perhaps wholly unexpected, which might even make the tender of a video record of interview or calling of a witness unfair. If the second question referred to the Full Court were understood literally as asking, at a point prior to trial, whether there will be a legal obligation for the prosecution to tender the video record of interview during the prosecution case at trial then the answer would be “Impossible to answer”.at 
However, his Honour was able to resolve the question by having regard to the manner in which the case was argued:
if the prosecutor were to maintain his stance throughout the Crown case of refusing to tender the video record of interview then it is likely that his conduct would be a breach of his duty of fairness and would lead to an unfair trial and a miscarriage of justice.at 
Justices Nettle and Edelman agreed with the orders proposed by the majority, and the appeal was unanimously allowed.
1. This is because if the evidence is adduced by the prosecution, the defence is then able to advance their case in a way which might not be possible if the defence was required to adduce it during examination-in-chief. For example, if, during the State case, the prosecution calls a witness, the defence is able to cross-examine that witness. This means the defence can ask the witness leading questions, and can challenge the witness’ credit by contradicting them.
2. To give an example, the judge might be unsure as to whether certain evidence is admissible. Generally trial judges are more likely to make their own evidentiary rulings, leaving an appeal against conviction as the only avenue for the correction of error.
3. Hearsay is a statement made outside court which is adduced in a trial in order to prove the truth of its contents. Hearsay is generally not admissible because it is not reliable: the statement having not been made on oath or affirmation, and its maker having not been subjected to cross-examination. There is a fear that hearsay statements may have been concocted, ‘made up’, or embellished. Admissions against interest are an exception to the rule because the law considers that they are unlikely to have been made up (that is, people tend not to make statements against their interest unless the statements are true).
4. These two words might send chills down the spines of experienced prosecutors. It is worth bearing in mind that the High Court has warned that the prosecution’s role is not one of securing convictions at all costs, but of ensuring a fair trial of the accused. Accordingly, the failure of the State to call a witness may, depending on the circumstances, give rise to a miscarriage of justice. A selection of cases discussing this important proposition are: R v Apostilides (1984) 154 CLR 563; Whitehorn v The Queen (1983) 152 CLR 657, 663-4 (Deane J), 674 (Dawson J); Ritchie v Western Australia  WASCA 134; (2016) 260 A Crim R 367, 375 ,  (McLure P); R v Livermore (2006) 67 NSWLR 659; Bugeja & Johnson v R (2010) 30 VR 493. For a very rare example of a case where a witness was called by the trial judge in order to ensure a fair trial, when the prosecution refused to call the witness, see R v Peros  1 Qd R 1.
5. See R v Nguyen  NTSC 37; (2019) 345 FLR 40.
This post is authored by Matthew Thompson and edited by Aidan Ricciardo.