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s 137 – Exclusion of prejudicial evidence in criminal proceedings

137 Exclusion of prejudicial evidence in criminal proceedings

In a criminal proceeding, the court must refuse to admit evidence adduced by the prosecutor if its probative value is outweighed by the danger of unfair prejudice to the accused.

Expressions defined in the Dictionary are identified in bold print. Click here to access the Dictionary.

Continuity and change – minor change

  1. Section 137 applies only to evidence adduced by the prosecution in criminal proceedings. A court must refuse to admit such evidence if its probative value is outweighed by the danger of unfair prejudice to the accused.

    Procedure

  2. A judge must first ascertain that an item of evidence is relevant in accordance with s55 and consider whether any of the exclusionary rules applies (IMM v R (2016) 257 CLR 300; [2016] HCA 14 at [37]-[41]).
  3. Then, if the evidence is relevant and not otherwise inadmissible and objection is taken, s137 requires the court to undertake a balancing exercise between the probative value of the evidence and the ‘danger of unfair prejudice’ to the accused.
  4. This balancing exercise requires the judge to separately assess the probative value of the evidence, followed by the danger of unfair prejudice, before weighing these two matters (Marsh v R [2015] NSWCCA 154 at [72]; R v Burton [2013] NSWCCA 335 at [134], [182]).
  5. In undertaking this evaluation of probative value, the High Court majority in IMM (French CJ, Kiefel, Bell and Keane JJ) explained:

    The enquiry for the purposes of s 55 is whether the evidence is capable of the effect described at all. The enquiry for the purposes of determining the probative value of evidence is as to the extent of that possible effect. But the point is that in both cases the enquiry is essentially the same; it is as to how the evidence might affect findings of fact. An assessment of the extent of the probative value of the evidence takes that enquiry further, but it remains an enquiry as to the probative nature of the evidence.

    The assessment of "the extent to which the evidence could rationally affect the assessment of the probability of the existence of a fact in issue" requires that the possible use to which the evidence might be put, which is to say how it might be used, be taken at its highest (IMM v R (2016) 257 CLR 300; [2016] HCA 14 at [43]-[44]).

  6. This exercise itself requires a clear identification of what “fact in issue” the evidence is relevant to prove, as that identifies the subject matter of the probative value of the evidence (R v Burton [2013] NSWCCA 335 at [148]).
  7. The majority in IMM v R (French CJ, Kiefel, Bell and Keane JJ) stated that:

    The use of the term "probative value" and the word "extent" in its definition rest upon the premise that relevant evidence can rationally affect the assessment of the probability of the existence of a fact in issue to different degrees. Taken by itself, the evidence may, if accepted, support an inference to a high degree of probability that the fact in issue exists. On the other hand, it may only, as in the case of circumstantial evidence, strengthen that inference, when considered in conjunction with other evidence. The evidence, if accepted, may establish a sufficient condition for the existence of the fact in issue or only a necessary condition. The ways in which evidence, if accepted, could affect the assessment of the probability of the existence of a fact in issue are various. Within the framework imposed by the statute and, in particular, the assumption that the evidence is accepted, the determination of probative value is a matter for the judge (IMM v R (2016) 257 CLR 300; [2016] HCA 14 at [45]).

    (i) Mandatory exclusion

  8. Notwithstanding this application of judgment, it has been said that the application of s137 is not a discretion (Em v R (2007) 232 CLR 67; [2007] HCA 46 at [95], [102] per Gummow and Hayne JJ).

    (ii) Acting on own motion

  9. In Steve v R [2008] NSWCCA 231 (in which case the accused was represented at trial), s137 was interpreted to require a trial judge to exclude evidence when its probative value is outweighed by the danger of unfair prejudice, notwithstanding that no objection has been taken to the evidence during the trial.
  10. This decision was subsequently considered but not followed in a criminal trial where the accused was represented (FDP v R (2008) 74 NSWLR 645; [2008] NSWCCA 317 at [21]-[30]). The Court reviewed the decisions and noted the interpretation of s137 in Steve v R was not strictly necessary for the decision. There remains an obligation to alert the parties in appropriate cases. See point (vi) under the heading Sections 135 and 137 Compared to the Introduction to this Part 3.11.

    (iii) Onus

  11. The accused bears the onus to persuade a trial judge that the danger of unfair prejudice from the evidence outweighs its probative value (R v Polkinghorne [1999] NSWSC 704 per Levine J; Gilmour v EPA; Tableland Topdressing v EPA (2002) 55 NSWLR 593; [2002] NSWCCA 399 at [46]; R v DG; DG v R (2010) 28 VR 127; [2010] VSCA 173 per Buchanan, Weinberg and Bongiorno JJA at [52]-[54]; Kuehne v R [2011] NSWCCA 101 at [21] per Hislop J (McColl JA and RS Hulme J agreeing)).

    The weighing exercise

  12. Courts have noted that the weighing exercise is difficult because it requires incommensurables for which there is no standard of comparison to be balanced – probative value goes to proof of issue, and prejudicial effect goes to fairness of the trial and, in criminal trials, to the risk of the misuse of the evidence by the jury (Pfennig v R (1995) 182 CLR 461; [1995] HCA 7 per McHugh J in respect of propensity evidence at [39]; R v DG; DG v R (2010) 28 VR 127; [2010] VSCA 173 per Buchanan, Weinberg and Bongiorno JJA at [51]).
  13. In the weighing exercise (for s135 and s137), the court should consider the extent to which the problems of admitting the evidence may be mitigated by actions other than exclusion – for example, by limiting the use of the evidence or by jury directions (see ALRC 26:1 at [644]; ALRC 102 at [16.34]; R v Shamouil (2006) 66 NSWLR 228; [2006] NSWCCA 112 at [72], [74], [77] referring to R v BD (1997) 94 A Crim R 131 at 151 (Simpson and Adams JJ agreeing); DPP (NSW) v JG [2010] NSWCCA 222 at [115]).

    Probative value

    (i) Definition

  14. ‘Probative value’ is defined in the UEA Dictionary as ‘the extent to which the evidence could rationally affect the assessment of the probability of the existence of a fact in issue’.
  15. The meaning of ‘probative value’ must be assessed in its legal and factual context. The:

    factors to be taken into account in determining whether a piece of evidence has the requisite degree of probative value or results in a degree of unfair prejudice will vary depending on the type of evidence and the context in which it is sought to be adduced (ALRC 102 at [3.31]).

  16. That is, the probative value of evidence varies according to the fact in issue which it is being used to prove and the reasoning relied on to prove that fact. For this reason, it has been described as a ‘floating standard’ (especially with respect to credibility, tendency and/or coincidence evidence, which work to relate to other evidence rather than being directly associated with a fact in issue) (see ALRC 102 at [3.31], [3.35]).
  17. The definition uses concepts similar to those used in the test for relevance – namely, whether the evidence ‘could rationally affect (directly or indirectly) the assessment of the probability of the existence of a fact in issue in the proceeding’ (s55)) – but it is expressed in terms of degree. Therefore, the probative value of evidence is assessed at least in part by reference to its degree of relevance to a fact in issue (R v Lockyer (1996) 89 A Crim R 457 at 459).

    (ii) Notions of reliability and credibility

  18. Intermediate appellate courts had taken two divergent approaches to the interpretation of the term ‘probative value’ and whether the court must take the reliability of evidence into account.
  19. In IMM v R (2016) 257 CLR 300; [2016] HCA 14, a majority of the High Court (French CJ, Kiefel, Bell and Keane JJ) held that the New South Wales approach is correct. The Court must take the evidence at its highest and consider the extent to which the evidence can affect the probability of the existence of the facts in issue (IMM v R (2016) 257 CLR 300; [2016] HCA 14 at [47]).
  20. The majority stated that the Uniform Evidence Law “was intended to make substantial changes to the common law rules of evidence. The statute’s language is the primary source, not the pre-existing common law” (IMM v R (2016) 257 CLR 300; [2016] HCA 14, [35]). Further, the majority stated that when assessing the probative value of evidence, the judge must assume that the evidence is accepted and, as a result, that the evidence is both credible and reliable (at [48]) and “no question as to credibility of the evidence, or the witness giving it can arise. For the same reason, no question as to the reliability of the evidence can arise” ([39], [52]).
  21. However, the majority recognised that there may be a limiting case in which the evidence is so inherently incredible, fanciful or preposterous that it could not be accepted by a rational jury. In such a case its effect on the probability of the existence of a fact in issue would be nil and it would not meet the criterion of relevance ([39]).
  22. The majority noted, however, that “taken by itself … evidence may, if accepted, support an inference to a high degree of probability that the fact in issue exists” or “may only strengthen the inference when considered in conjunction with other evidence” ([45]).
  23. In the course of its overall assessment of the probative value of the two items of evidence in question in that case (the “tendency’’ and “ complaints” evidence), the majority looked at other evidence received in the trial which was relevant to the probative value of the evidence in question (see, e.g., [62] – [64], [68] – [70] and [73). It did not, however, indicate whether such other evidence also had to be assumed to be reliable and credible when making this assessment.
  24. The rule of taking evidence at its highest was reiterated in the unanimous judgment in R v Bauer [2018] HCA 40 at [95]:

    [I]t is not for a trial judge to say what probative value a jury should give to evidence but only what probative value the jury acting rationally and properly directed could give to the evidence. Hence, unless evidence is so lacking in credibility or reliability that it would not be open to a jury acting rationally and properly directed to accept it, the probative value of the evidence must be assessed, for the purposes of s 137, at its highest

  25. Prior to IMM several associated issues were identified as potentially affecting the assessment of probative value. These are:

    Reliability, credibility and identification evidence; assessing probative value

  26. In the course of the decision in IMM the majority considered an example of identification evidence given by JD Heydon QC where the identification was made “briefly in foggy conditions and in bad light by a witness who did not know the person identified”. The majority stated:

    As he points out, on one approach it is possible to say that taken at its highest it is as high as any other identification, and then look for particular weaknesses in the evidence (which would include reliability). On another approach, it is an identification, but a weak one because it is simply unconvincing. The former is the approach undertaken by the Victorian Court of Appeal; the latter by the New South Wales Court of Criminal Appeal. The point presently to be made is that it is the latter approach which the statute requires. This is the assessment undertaken by the trial judge of the probative value of the evidence ([50]).

  27. This example was also cited with approval by the Gageler J in his dissenting judgment in IMM v R (see [92] per Gageler J) and similar concerns identified by Nettle and Gordon JJ at [147]. The example was also adopted by the Victoria Court of Appeal in Bayley v R [2016] VSCA 160 at [51]-[55].
  28. This suggests that in relation to identification evidence, an assumption of reliability in relation to the evidence in question does not require the judge to overlook other evidence that points to flaws in the evidence in question in assessing its probative value - for example, in relation to identification evidence, evidence of a risk of displacement or suggestion.
  29. While the High Court in R v Bauer [2018] HCA 40 reiterated the requirement that judges must take evidence at its highest when assesing probative value, the Court did not revisit or explain how to take into account flaws in an identification.

    Reliability, credibility and previous representations – assessing probative value.

  30. In IMM v R (2016) 257 CLR 300; [2016] HCA 14, the majority considered the probative value of the complainant’s previous representation and concluded:

    The complaint evidence was tendered for the purpose of proving the acts charged. Given the content of the evidence, the evident distress of the complainant in making the complaint and the timing of the earlier complaint, it cannot be said that its probative value was low. It was potentially significant ([73]).

  31. This process of considering the content of the evidence, the distress and the timing of the complaint suggest that there are limits to how the assumption of reliability and credibility of evidence operates in relation to previous representations.

    Reliability, credibility and tendency evidence-assessing probative value

  32. In IMM v R (2016) 257 CLR 300; [2016] HCA 14 at [61]-[63], the majority held that the complainant's account of an uncharged act did not have significant probative value because it came from the complainant and there were no special features to lend it support.
  33. This approach was qualified in R v Bauer [2018] HCA 40 as confined to cases where the uncharged act was remote in time and of significantly different gravity to the charged acts. Where the alleged offending occurred over a period, and the uncharged acts relate to conduct of a similar character that was committed at the same time, there is no need for special features before the evidence is significantly probative in relation to offences against that complainant ([48]-[62]).
  34. See, further, s 97, s 98 – Civil and criminal proceedings: the tendency rule and the coincidence rule.

    Reliability and scientific evidence – assessing probative value

  35. Prior to IMM v R (2016) 257 CLR 300; [2016] HCA 14, the Victorian Court of Appeal held that the reliability of opinion evidence does not form part of the assessment of whether the evidence is admissible under an exception to the opinion rule, such as s79. Instead, reliability is relevant in an assessment in considering the admissibility of scientific opinion evidence under sections 135 or 137 (Tuite v R (2015) 49 VR 196; [2015] VSCA 148).
  36. In Tuite v R the Court acknowledged the risk of a jury being misled by junk science: Dressed up in scientific language which the jury does not easily understand and submitted through a witness of impressive antecedents, this evidence is apt to be accepted by the jury as being virtually infallible and as having more weight than it deserves (R v Mohan [1994] 2 SCR 9, 21).
  37. To address this risk, the focus of the court’s attention in assessing the reliability should be proof of validation. “Ideally there should be proof of both in-house validation and independent external validation”, though the commercialisation of forensic science can make external validation difficult (Tuite v R (2015) 49 VR 196; [2015] VSCA 148, [101]-[102]).
  38. When discussing reliability in this context, it is important to distinguish between the reliability of the underlying science and the reliability of the particular methodology or theory which is the basis for the expert’s opinion (Tuite v R (2015) 49 VR 196; [2015] VSCA 148, [90]). In that case, it was held that evidence of validation of both was relevant to the issue of the reliability of the opinion (at [11]).
  39. Requiring validation has the following advantages: 
  40. Where evidence is sought to be led on the basis of so-called ‘new science’, then the party seeking to lead the evidence will need to call appropriate evidence of reliability to show that the science is sufficiently reliable to be used by a court (Tuite v R (2015) 49 VR 196; [2015] VSCA 148, [106] citing R v Trochym [2007] 1 SCR 239, [33]).
  41. Validation studies may need to address questions such as (see DPP v Tuite [2014] VSC 662, [60]-[78] and Tuite v R (2015) 49 VR 196; [2015] VSCA 148, [117-118]):
  42. As the Victorian Court of Appeal (Maxwell P, Redlich and Weinberg JJA) stated in Tuite v R:

    The lack of validation is at the forefront of the critique of forensic science advanced by Professor Edmond and others. The concerns expressed in the reports referred to earlier must be taken very seriously. We note, in particular, the 2009 conclusion of the US National Academy of Sciences that with the exception of nuclear DNA analysis, … no forensic method has been rigorously shown to have the capacity to consistently, and with a high degree of certainty, demonstrate a connection between evidence and a specific individual or source (Tuite v R (2015) 49 VR 196; [2015] VSCA 148, [107] (footnotes omitted)).

  43. The reasoning in Tuite depended, in part, on the principle from Dupas v R (2012) 40 VR 182; [2012] VSCA 328 that considerations of reliability affect the assessment of probative value of the evidence of a witness. The High Court stated in IMM v R [51] – [52] that

    At a practical level, it could not be intended that a trial judge undertake an assessment of the actual probative value of the evidence at the point of admissibility ……

    Once it is understood that an assumption as to the jury’s acceptance of the evidence must be made, it follows that no question as to credibility of the evidence, or the witness giving it, can arise. For the same reason, no question as the reliability of the evidence can arise. If the jury are to be taken to accept the evidence, they will be taken to accepted completely in proof of the facts stated. There can be no disaggregation of the two – reliability and credibility – as Dupas v R may imply. They are both subsumed in the jury’s acceptance of the evidence.

  44. As the High Court confirmed in R v Bauer [2018] HCA 40 at [95], evidence may be excluded as lacking probative value when it is so lacking in credibility or reliability that a properly instructed rational jury could not accept it. This approach to the exclusionary rule shows that a court can reject scientific evidence which is completely lacking reliability.

    Danger of unfair prejudice

    (i) Meaning of ‘unfair prejudice’

  45. ‘Unfair prejudice’ is not defined in the Act. ALRC 26:1 indicates it is intended to cover evidence which could introduce adverse and ‘irrational’ considerations or cause jurors to accord other evidence more probative value than it deserves (at [644]).
  46. Subsequent consideration of whether to provide a legislative definition led the Commissions to conclude that to do so risks narrowing the grounds of exclusion under s135 and s137 and thereby fettering the application of the sections (ALRC Discussion Paper 69 at [14.47], [14.60]).
  47. Part 3.11 requires not ‘prejudice’ but ‘unfair prejudice’. Unfair prejudice will arise if there is real risk it ‘will be misused by the jury in some unfair way’ (R v BD (1997) 94 A Crim R 131 at 139 per Hunt CJ at CL; approved in Papakosmas v R (1999) 196 CLR 297; [1999] HCA 37 at [91] per McHugh J). This is consistent with the approach taken at common law (Dupas v R (2012) 40 VR 182; [2012] VSCA 328 at [175]).
  48. Circumstances in which concerns regarding ‘unfair prejudice’ may arise include where there is a danger that the jury will misjudge the weight to be given to particular evidence or engage in an illegitimate form of reasoning because, for example, of the prejudicial impact of evidence of other criminal acts. The risk of unfair prejudice can also arise where there is an inability to test the evidence, or where the evidence will be incomplete (Dupas v R (2012) 40 VR 182; [2012] VSCA 328 at [175], citing R v Darmody (2010) 25 VR 209; [2010] VSCA 41; DPP (NSW) v JG [2010] NSWCCA 222 at 121 per Basten JA; DPP v Kerr [2015] VSC 65 at [17]).
  49. Evidence will not be unfairly prejudicial merely because it increases the likelihood of an accused person being convicted (see, e.g., FMJ v R [2011] VSCA 308 at [56] per Weinberg JA (Hansen JA and Beach AJA agreeing); Dupas v R (2012) 40 VR 182; [2012] VSCA 328 at [175]).
  50. In assessing the asserted ‘unfair prejudice’, it is open to the court to consider the weight of the evidence (R v Mundine [2008] NSWCCA 55 at [44] per Simpson J (McClellan CJ at CL and Grove J agreeing)).

    (ii) ‘The danger’

  51. The danger cannot be merely a risk or a possibility – there must be a real danger of unfair prejudice arising in the event that the evidence is admitted. There ‘must be a real risk that the evidence will be misused by the jury in some way and that that risk will exist notwithstanding proper directions’ (R v Shamouil (2006) 66 NSWLR 228; [2006] NSWCCA 112 at [72] per Spigelman CJ; Dupas v R (2012) 40 VR 182; [2012] VSCA 328 at [175]).
  52. In Papakosmas v R (1999) 196 CLR 297; [1999] HCA 37, the Court emphasised that the mere fact that evidence would not have been admissible at common law does not create unfair prejudice of itself.

    (iii) Procedural unfairness

  53. Despite early views that ‘unfair prejudice’ did not extend beyond the tribunal of fact misusing evidence to procedural unfairness (see, for example, Papakosmas v R (1999) 196 CLR 297; [1999] HCA 37 per McHugh J at [93], [97]), it is now generally accepted that procedural considerations may constitute unfair prejudice. Cases supporting that proposition include:
  54. Victorian cases also support this approach. In R v Darmody, the Court of Appeal 'assumed' that forensic disadvantages may constitute unfair prejudice (R v Darmody (2010) 25 VR 209; [2010] VSCA 41 at [45]). In DPP v Curran (Ruling No 1), Kaye J accepted that procedural disadvantage may constitute unfair prejudice, while noting that there had been some conflict on the question (DPP v Curran (Ruling No 1) [2011] VSC 279 at [53]; see also acceptance of this proposition by J Forrest J in Matthews v SPI Electricity Pty Ltd & Ors (Ruling No 35) [2014] VSC 59 at [51]-[65]).
  55. However, unfair prejudice is not so wide as to cover all notions of an unfair trial. Evidence may fall between the protections of ss90, 137 and 138 and yet admission of such evidence may give rise to a risk of an unfair trial. In such circumstances, the court has a residual common law discretion to exclude evidence in order to ensure a fair trial (Haddara v R (2014) 43 VR 53; [2014] VSCA 100; see also Police v Dunstall (2015) 256 CLR 403; [2015] HCA 26 and s 11 - General powers of a court). Examples of such evidence may include non-admission statements made in a police interview where the accused did not have the intellectual capacity to exercise the right to silence (Haddara v R (2014) 43 VR 53; [2014] VSCA 100) or evidence that controverts a previous acquittal (Ulutui v R (2014) 41 VR 676; [2014] VSCA 110).
  56. Procedural unfairness may arise in a number of ways, including:

    Where hearsay evidence cannot be cross-examined

  57. A degree of prejudice is inevitable where hearsay evidence cannot be cross-examined. However, an inability to cross-examine the maker of a hearsay statement is not of itself necessarily so unfairly prejudicial that it outweighs the probative value of the evidence, or makes the trial unfair (Bray v R (2014) 46 VR 623; [2014] VSCA 276; cited in Fletcher v R (2015) 45 VR 634; [2015] VSCA 146) [81]- [85]).
  58. Thus an inability to cross-examine the maker of a hearsay statement does not of itself justify excluding the evidence (Ordukaya v Hicks [2000] NSWCA 180 at [38]-[41] per Sheller JA (Meagher JA concurring); R v Sutekski (2002) 56 NSWLR 182; [2002] NSWCCA 509 at [126]-[127] per Wood CJ at CL).
  59. Instead, each case must be determined on its facts, with regard to the nature of the evidence and extent to which the other party would be unfairly prejudiced by its admission (R v Sutekski (2002) 56 NSWLR 182; [2002] NSWCCA 509 at [126]-[127] per Wood CJ at CL; Galvin v R [2006] NSWCCA 66 at [40] per Howie J (McClelland CJ at CL and Latham J agreeing)).
  60. In assessing the risk of unfair prejudice associated with hearsay evidence which cannot be cross-examined, the Court may take into account the extent to which cross-examination of other witnesses can assist in challenging the hearsay evidence (R v Tai (2016) 93 NSWLR 404; [2016] NSWCCA 207 at [44]-[45]).
  61. The Full Federal Court has suggested that, in a limited range of cases, an inability to ‘effectively’ cross-examine may constitute unfair prejudice. However, the Court also suggested that ordinary risks associated with cross-examination, including the possibility of helping an opponent make out their case, are simply strategic risks, and not forensic disadvantages (La Trobe Capital & Mortgage Corp Ltd v Hay Property Consultants Pty Ltd (2011) 190 FCR 299; [2011] FCAFC 4 at [66]-[73]).

    (iii) Other provisions to mitigate unfair prejudice

  62. With respect to s137 and s135, the potential for unfair prejudice should be considered in the context of whether it could be mitigated by other action such as:
  63. In respect of identification evidence, it has been noted that:

    Appropriate warnings are generally likely to remove any real risk of identification evidence being given greater probative value than the evidence deserves. Whether the trial judge should conclude that the warnings will do so requires some evaluation of the probative value which the jury could reasonably assign to that evidence and an assessment of the risk that, notwithstanding appropriate warnings, the jury may attach greater weight to that evidence than it should receive (Dupas v R (2012) 40 VR 182; [2012] VSCA 328 at [177]).

    Appellate review

  64. Section 137 requires a weighing process/evaluation, the outcome of which determines whether or not the evidence is admissible (i.e. the provision is not a discretion). The standard of appellate review of decisions under this section varies depending on whether the review is carried out on an interlocutory appeal or an appeal from a final decision.
  65. In R v Ford [2009] NSWCCA 306, the NSW Court of Criminal Appeal held that where the facts have been established or are undisputed:

    an appellate court is in as good a position as the trial judge to make that particular decision and thus conclude that the trial judge was in error (R v Ford [2009] NSWCCA 306, citing Warren v Coombes (1979) 142 CLR 531 at 551; [1979] HCA 9).

  66. This decision was upheld as correctly stating the approach to review of a decision on a final appeal in Victoria in McCartney v R (2012) 38 VR 1; [2012] VSCA 268 (see also Riley v R [2011] NSWCCA 238 at [161]-[162] per McClellan CJ at CL (Hoeben J and Grove AJ agreeing)).
  67. However, where a decision under s137 is challenged on an interlocutory appeal, the trial judge’s evaluation must be reviewed in accordance with the principles from House v The King (KJM v R (No 2) (2011) 33 VR 11; [2011] VSCA 268; DAO v R (2011) 81 NSWLR 568; [2011] NSWCCA 63; see also MA v R (2011) 31 VR 203; [2011] VSCA 13; Singh v R (2011) 33 VR 1; [2011] VSCA 263).

    Significant other sections that are or may be relevant

Last updated: 20 September 2018

See Also

Part 3.11: Discretionary and Mandatory Exclusions (ss 135 – 139)

s 135 – General discretion to exclude evidence

s 136 – General discretion to limit use of evidence

s 138 – Exclusion of improperly or illegally obtained evidence

s 139 – Cautioning of persons