New arrivals to the arena of criminal law are sometimes surprised to learn that evidence which is improperly or unlawfully obtained by investigators is not — for that reason alone — inadmissible.

Historically, the default position has been that relevant evidence is admissible unless made inadmissible by statute or an exclusionary rule of evidence. The touchstone of confessional evidence was always reliability, not fairness. Principles regulating the exercise of judicial discretion to exclude evidence have developed significantly over the last century as ideas of justice, individual rights and the role of courts have evolved.

Further, the courts have traditionally adopted a tolerant approach to behaviour by police that might be regarded as sneaky or underhanded, without deeming it to be improper. In Tofilau v The Queen police pretended to be members of an underworld gang, even committing staged “crimes” to gain the trust of suspects and elicit admissions from them for offences. The High Court, though with obvious reservation, found that such trickery was acceptable:

[416] Nothing said above should be taken as a warrant for any undiscriminating reception of evidence gathered by police officers operating covertly. Plainly, as these appeals show, it is desirable that covert operations be undertaken from time to time, and they can be undertaken without damaging the integrity of the police force, or indeed of the system of criminal justice itself. Covert operations can however be risky. Sometimes the covert officers will, as a matter of necessity, be remote from close supervision and the discipline that it entails. Seduction of officers by criminals is not unknown. Covert officers can be placed in danger. Their response to that danger may cause them, however understandably, to act in a way that might otherwise be thought irregular. But none of those factors were present in the circumstances out of which these appeals arose. The trial judges in these cases were in all respects careful and discriminating in considering and admitting the relevant evidence.

There’s been debate about how many types of discretion to exclude there are, and whether some should be considered sub-categories of others. Three broad categories have been reproduced in statutory form in the Evidence Act 2008:

• The fairness discretion (the R v Lee and R v Ireland discretion about admissions, found at s 90)
• The unfair prejudice discretion (the Christie discretion, now at s 137)
• The public policy discretion (outlined in Bunning v Cross, now in modified form at s 138)

The new Evidence Act will confer other specific powers and obligations on a court considering admissibility (notably ss 84 and 85 about the admissibility of confessions and admissions), but those three are the general discretions to exclude evidence.

Section 138 has been discussed here before. It’s been in force for over ten years in New South Wales, giving the courts there opportunity to consider its implications. In R v Helmhoudt, the NSW Court of Appeal dealt with inadvertent non-compliance with regulations governing the treatment of people in custody. The Court decided the onus of proving unlawful or or improper conduct lay on the accused, on the balance of probabilities: R v Coulstock (1998) 99 A Crim R 143. Once satisfied, the onus then shifts back to the prosecution to prove that, despite the impugned conduct, the evidence should nonetheless be admitted. If the prosecution can’t do that, the evidence will be excluded.

In Fleming v R, the behaviour of the police was far more deliberate, though not contrary to any specific statute or rule.

The investigation was a cold case. It was reopened to discover if advances in technology could lead to the identification of the offender. A DNA sample was taken from the deceased victim of a sexual assault and murder in NSW in 1984. At the time the investigation was re-opened, the suspect lived in rural Victoria. Neither Victorian nor NSW law provided for taking a DNA sample that might prove or disprove his involvement in the offence. (But it later emerged that the sample could have been taken if an outstanding warrant had been executed and the suspect extradited to NSW).

A Victorian policeman met with the accused under the pretext of investigating a local complaint about an unrelated matter. The suspect was asked to draw a diagram, and while doing so he dribbled on the paper he was drawing on. The paper was sent to NSW and analysed: the DNA matched the sample taken from the victim.

The evidence was challenged under s 138 at trial, but admitted. The trial judge ruled that taking the sample by trickery wasn’t unlawful or improper, and that even if thought it was, the desirability of admitting the evidence outweighed the desirability of excluding it (relying on s 138(3).)

The accused was convicted and appealed.

At the appeal, McClellan CJ at CL said:

[17] Impropriety is not defined in the Evidence Act. In Ridgway v The Queen (1984) 184 CLR 19, a case before the Evidence Act was enacted, Mason CJ, Deane and Dawson JJ said, at 37, that “the stage of impropriety will be reached in the case of conduct which is not illegal only in cases involving a degree of harassment or manipulation which is clearly inconsistent with minimum standards of acceptable police conduct in all the circumstances.” Their Honours acknowledged that the effective investigation by police may involve subterfuge and deceit and may extend to the intentional creation of opportunities for the commission by a suspect of a criminal offence. Their Honours acknowledged that “a finding that law enforcement officers have engaged in … clearly improper conduct will not, of course, suffice of itself to give rise to the discretion to exclude evidence of the alleged offences or of an element of it.” Their Honours accepted that deceptive tactics, which do not involve illegal conduct, will ordinarily be legitimate.

The Court of Appeal referred to its previous comments in R v Camalleri (2007) 169 A Crim R 197:

[31] As Howie J made plain in R v EM (2003) NSWCCA 374 at [74] – [78], s 138 is concerned with balancing public interests. The prejudice to the individual accused, which to varying degrees must be present in every case, will rarely be material. It may be of concern if the means by which the evidence was obtained has the consequence that an accused cannot effectively respond to it. There may be other personal considerations in a particular case. However, the fundamental concern of the section is to ensure that, if the law has been breached, or some other impropriety has been involved in obtaining the evidence, this is balanced against the public interest in successfully prosecuting alleged offenders. The competing interests are obedience to the law in the gathering of evidence and enforcement of the law in respect of offenders.

The appeal was dismissed. Whether a Victorian Supreme Court would rule the same way remains to be seen. But given that it concerns identical legislation, it appears likely.