Tuesday, September 15, 2020

Probative value and reliability - the evidence of prison informants

The idea of “probative value” in s 8 of the Evidence Act 2006 came under scrutiny, and was the subject of some disagreement, in Roigard v R [2020] NZSC 94 (14 September 2020).


My impression is that this case misses the critical thing about s 8 in this context: it should be all about whether admission of the challenged evidence would have an unfairly prejudicial effect on the proceeding.


The evidence will have probative value, otherwise it would be inadmissible under s 7.


Whether the probative value is “outweighed” by the risk of unfair prejudice is not a matter of balancing (a word not used in s 8 and one which, as I have argued, introduces an inappropriate metaphor). Outweighed here should mean that, in context, the risk of unfairness posed by admission of the evidence is unacceptable in the sense that it would not be overcome by appropriate cross-examination or by directions the judge could give the jury.


In Roigard only brief attention is given to unfair prejudice, identifying the danger as the risk that the jury would “overweight” the prosecution evidence: per Winkelmann CJ and Brown J at [156]. The Judges all agreed that in cases like this, where prisoners give evidence about confessions allegedly made to them by the defendant, it is necessary to formulate guidance for prosecutors and to keep a register of such witnesses’ convictions and rewards for giving such evidence.


The judicial disagreement was over the criteria for assessing probative value, with the result that the dissenting Judges would have excluded the evidence of one of the two challenged witnesses. Regarding the risk of unfairness as the same for each witness, the dissenting Judges considered that one witness was so lacking in credibility that the risk of unfairness outweighed the probative value of his evidence.


The disagreement in this case is all about probative value. The majority Judges took a narrower view of what reliability factors are relevant to assessing probative value under s 8 than did the minority.


But as I have said, it doesn’t matter how probative evidence is, if its admission would cause unfairness.

What is probative value, and does it include reliability?


A fact-finder in a trial must decide, when the time comes to reach a verdict, whether to accept a witness’s evidence. Is the witness reliable? Is the witness truthful, and, if truthful, nevertheless possibly mistaken? These considerations are matters of credibility.


If the fact-finder decides to accept what the witness says, the next question is how much probative value that testimony has. Probative value is a quality that attaches to evidence that is accepted. In a criminal trial, the probative value of evidence for the prosecution is a comparison of the extent to which the evidence is consistent with guilt or with innocence.


There can be occasions where a witness gives evidence about the reliability of testimony. For example, a witness may say that the error rate in DNA testing is x%. The fact-finder will take this into account in deciding whether to accept the evidence of a match. This is different from deciding the probative value of the evidence of a match. The probability of a match may be very high, so the witness’s evidence that there was a match will be credible. But the significance of the match in the circumstances of the case may be much lower, as for example where there are innocent explanations for the presence of the defendant’s DNA at the crime scene. Here, the probative value of the evidence of a match would be lower than where there is no apparent innocent explanation.

The risk of error can be relevant to probative value. The error may exaggerate the consistency of the evidence with guilt and minimise its consistency with innocence. Reliability has two roles: first in relation to the credibility of testimony, and secondly in relation to the probative value of testimony that has passes the credibility threshold.


There are no standards of proof at play here. It is sufficient that the fact-finder is satisfied that testimony is credible and that it has a probative value which is for the fact-finder to assess. The verdict depends on whether the fact-finder decides that the combined probative values of the accepted evidence reaches the criminal standard of proof.


Applying these thoughts to Roigard: the testimony in question was that the defendant confessed guilt independently to each of the two witnesses while in custody awaiting trial. The first question for a fact-finder (juror) is whether the testimony is credible: did the defendant make the statements reported by each witness? Reliability considerations relevant here were ones of self-interest: what did each witness have to gain from testifying, and was each witness a truthful person?


It might have been quite unlikely that a fact-finder would accept any of the contested evidence here. But that would be for the fact-finder unless the evidence was so incredible that it would be irrational to believe it, in which event a judge could rule it inadmissible because it had no probative value and so was irrelevant in terms of s 7.


If a fact-finder did accept the evidence here as being credible, then the question of its probative value would have to be considered. A voluntary confession would have a high probative value. It would necessarily be reliable (unless made to protect another person, which was not an issue here), and it would be highly consistent with guilt and inconsistent with innocence. Note that here – where credibility is accepted - it is the reliability of the confession, not the reliability of the witness, that is relevant.


But where the fact-finder thinks the evidence was quite likely to be credible, but also possibly not credible, the acceptance of the evidence may be qualified or hesitant. The reduced reliability of the evidence could be reflected by a reduction in the fact-finder’s assessment of the probative value of the evidence.


None of these considerations directly address unfair prejudice to the defence. Unfair prejudice would exist to the extent that the defendant was unable to test the credibility of the witnesses by exploring the circumstances that gave rise to their self-interestedness and by examination of relevant previous convictions. Judicial directions, based where appropriate on psychological studies, could assist in reducing the risk that the fact-finder would too readily accept the credibility of the witnesses. The courts have not yet gone so far as to require that the fact-finder be satisfied beyond reasonable doubt that a confession was made. Unfair prejudice would also exist to the extent that the defendant was unable to properly challenge the probative value of the evidence, although here this is less important because a voluntary confession would necessarily have a high probative value. Even where the fact-finder discounts the probative value of a confession because of some doubts as to whether it was made, it would still have a probative value sufficient to affect the assessment of the overall strength of the prosecution case.