The admissibility of improperly obtained evidence is governed by section 30. The section applies to all evidence offered by the prosecution at trial. When a judge finds that evidence has been improperly obtained the judge must consider whether its exclusion is proportionate to the impropriety. This must be done by a balancing process that "gives appropriate weight to the impropriety and takes proper account of the need for an effective and credible system of justice". A non-exhaustive list of factors is included in section 30(3) and these may be taken into account by the judge in the balancing process.

Section 30 (3) Factors:

There is currently a degree of uncertainty as to how the section 30 test is to be applied, particularly in relation to the weight, interpretation and application of the relevant factors listed in section 30(3).

We are considering whether the Act should be amended to provide more guidance in this area, for example by clarifying: whether the centrality of evidence to the prosecution case is a relevant factor favouring admission; how the "seriousness" of an offence is to be determined and whether this factor favours exclusion or admission; whether the availability of alternative techniques favours admission or exclusion; and whether the absence of alternative techniques has any bearing on the section 30(2) balancing exercise.

These issues also raise a broader question as to whether section 30 should provide more prescriptive guidance as to its application, or whether a degree of indeterminacy in the statute is necessary in order to accommodate the necessarily fact-specific and evaluative nature of the section 30 balancing process.