Reforming Scots Criminal Law and Practice: The Carloway Report



9.1 The requirement for corroboration of evidence in criminal cases is an ancient and highly distinctive feature of Scots criminal law. Generally speaking, it is not used in other countries. The Carloway Report provides a description of the rule:

"there must first be at least one source of evidence (i.e. the testimony of one witness) that points to the guilt of the accused as the perpetrator of the crime. That evidence may be direct or circumstantial. Secondly, each "essential" or "crucial" fact, requiring to be proved, must be corroborated by other direct or circumstantial evidence (i.e. the testimony of at least one other witness)."5

9.2 The requirement for corroboration does not therefore require every fact in a case to be proved by two witnesses: "Corroboration is about the number of witnesses available to prove facts. It is not about number of facts available to prove guilt."6

Examples of corroboration

  • DNA: a forensic sample can be the only evidence required to identify a perpetrator, but there must be two 'witnesses' to: (a) the finding of the sample at the crime scene; (b) the obtaining of a sample from the accused; and (c) the comparison between those two samples.7
  • Eyewitnesses: if one witness states that he or she saw the accused commit a crime, this could be corroborated by testimony from another witness if it is sufficiently similar or consistent to confirm the testimony of the first witness. The evidence of the second eyewitness is needed to support that of the first witness and need not be directly incriminating on its own.
  • Eyewitness/circumstantial: where one witness states that he or she saw the accused commit a crime, this could be corroborated by circumstantial evidence confirming or supporting the eyewitness' evidence.
  • Circumstantial: In some cases a combination of circumstantial evidence from two or more sources can provide corroboration.

9.3 Historically, the requirement for corroboration has been regarded as an important protection against an accused person being convicted unsafely on the basis of the evidence of a dishonest or mistaken witness.

Lord Carloway's recommendations:

  • the current requirement for corroboration in criminal cases be abolished; and
  • in solemn prosecutions where there is no corroboration of testimony, there should be no requirement on the judge to warn the jury of any dangers perceived purely as a consequence of the absence of such corroboration.


9.4 Chapter 7 of Lord Carloway's Report charts in detail the origins and development of Scots law in relation to corroboration. It notes that the rule has its origins in a different era: one that featured capital punishment, little or no scientific evidence and an unstable legal profession. It concludes that the rule has developed so that it no longer requires "two testimonies, each confirming guilt. It requires one such testimony and another witness speaking to facts which make the truth or accuracy of the first witness's evidence more likely."8

9.5 The Report finds no evidence to support the argument that the requirement for corroboration protects against unsafe convictions. It suggests that instead of focusing on the quality of evidence, the requirement simply assesses the quantity of evidence. The Report concludes that the requirement for corroboration could itself lead to miscarriages of justice, by making it too difficult to prosecute certain offences, for example those typically committed in private (such as rape). Research conducted for the Carloway Report examined 458 serious criminal cases that did not make it to trial in the year 2010. The cases were discontinued after an initial court appearance. The research found that 268 of those cases (58.5%) would have had a 'reasonable prospect of conviction' (the assessment used by prosecutors in England and Wales) had there been no corroboration test. The Carloway Report also contains research focused on sexual offences where there was insufficient evidence to allow proceedings on petition (an earlier stage). This research examined 141 sexual offence cases dropped in the period July to December 2010. It concluded that 95 (67%) of those cases would have had a reasonable prospect of conviction without the requirement for corroboration. The implication is that around 450 additional serious cases would have been prosecuted in court, although it is important to note that in cases which went to trial ultimately a jury would have decided whether to convict. There is therefore no guarantee that the number of convictions would increase to the same extent.

9.6 The Report concludes:

"…the requirement of corroboration should be entirely abolished for all categories of crime. It is an archaic rule that has no place in a modern legal system where judges and juries should be free to consider all relevant evidence and to answer the single question of whether they are satisfied beyond reasonable doubt that the accused person committed the offence libelled."9

9.7 Lord Carloway reaches a further recommendation to build upon the abolition of the requirement for corroboration. This seeks to guard against a possible practice that could potentially arise as a result of abolition. It could occur in situations where a trial judge might feel obliged to issue a special warning to the jury about the dangers of convicting on the basis of uncorroborated evidence. Although the Report acknowledges that a warning might in some cases be appropriate, it concludes that it should never be given automatically, either in all cases or in certain types of case. The trial judge should not feel compelled to issue a warning, but should instead be free to use his or her discretion depending upon the circumstances.

Response to recommendations

9.8 The recommendation on corroboration featured heavily in the Parliamentary debate on 1 December and in the Justice Committee's three evidence sessions on the report. Those sessions were summarised by the Committee in a letter to the Cabinet of Secretary for Justice dated 26 January 2012.

9.9 The recommendation to remove the requirement for corroboration has attracted a broad range of comment. Some have been strongly opposed to removal, with a common objection being that corroboration provides a safeguard against unsafe convictions. On the other hand, a significant body of opinion has agreed that there is a case for abolition. As noted by the Justice Committee,10 there appears at the very least to be a clear consensus that the use of corroboration rules in Scots criminal law should be reassessed. Commentators have also made reference to the removal of the requirement for corroboration in civil cases by the Civil Evidence (Scotland) Act 1988.

9.10 Regardless of their standpoint on abolition, many commentators have called for further consideration of its impact on other aspects of criminal evidence and procedure. There have been some suggestions that abolition would increase the number of prosecutions overall. However, Lord Carloway commented to the Justice Committee on 29 November11 that he would not expect the total number of prosecutions to increase if the requirement for corroboration were to be abolished. He did though suggest that there might be an increase in conviction rate.

Sexual offences

9.11 A feature of sexual crime is that it is typically committed in private, where corroboration may be difficult to obtain. Removal of the requirement for corroboration should therefore permit a higher number of prosecutions. In considering sexual offences, the Faculty of Advocates cautioned that "the abolition of corroboration might lead to more rape prosecutions but not necessarily more convictions".12 The Senators of the College of Justice also stressed this point in their submission in response to Lord Carloway's consultation paper.13 However, Rape Crisis Scotland argued in favour of abolition in writing to the Justice Committee. This view was particularly influenced by experiences following the 2010 Cadder decision. Rape Crisis Scotland contended that changes made as a result of Cadder had resulted in a significant drop in the number of rape prosecutions.14

9.12 Rape Crisis Scotland did also sound a note of caution, highlighting that other systems without a corroboration requirement, such as England and Wales, have a conviction rate for rape that is comparable to that in Scotland. It concluded that:

""Removing the requirement for corroboration does not mean there will be a flood of cases with very little evidence making it to court, or an unacceptable risk of miscarriages of justice. There will still be a test against which cases will be judged before they can proceed to court, but it will be one based on the quality of the evidence, not the quantity. Removing the requirement for corroboration should, however, enable the Crown to bring prosecutions in cases where there is a lack of corroboration but where they believe there is still enough evidence to give a reasonable chance of conviction."15

Juries and verdicts

9.13 The concern most frequently cited in relation to corroboration has been the interaction with the jury system, which permits a decision on conviction or acquittal to be made by a simple majority (8 out of 15 jurors). Only the most serious cases require to be tried before a jury in Scotland, making up less than 5% of all cases, with the remainder decided by a judge alone.

9.14 Scots criminal law is unusual in permitting a simple majority of jurors to convict or acquit. Most other Western systems that use juries rely upon unanimity or a qualified majority for a conviction. However, guilty verdicts in Scotland are reached on the basis that the key evidence has been corroborated. If the requirement for corroboration was to be removed and no further change made, it would become possible for 8 out of 15 jurors to convict an accused on the basis of uncorroborated evidence. Each justice system is different and direct comparisons of individual features can be misleading. Nevertheless, some have questioned whether such a system would retain adequate safeguards against wrongful conviction.16

9.15 Lord Carloway's terms of reference did not extend to consideration of the majority necessary for a conviction by a jury. However the Review did conclude that it did not regard an alteration as "either necessary or desirable."17 Nevertheless, Lord Carloway did make the following remark in evidence to the Justice Committee:

"If Parliament wishes to examine the majority verdicts and the not proven verdict, it is of course free to do so. I am not saying that it should not be changed; I am just saying that we did not think that it was directly connected."18

9.16 Lord Carloway went on to highlight that in other jury systems a failure to arrive at a verdict does not result in an acquittal. For example in England and Wales, a minimum of 10 out of 12 jurors is required to convict or acquit, but if a jury is unable to reach a decision, the accused is not acquitted. Instead, a decision has to be made about a retrial. Scotland does not operate retrials in this way and there are no 'hung juries': the agreement of 8 jurors is required for a conviction, otherwise the accused is acquitted.

9.17 There are two acquittal verdicts possible under Scots law: not proven and not guilty. A not proven verdict has the same status in law as a verdict of not guilty. Some commentators have suggested that removal of the corroboration requirement would impact upon use of the 'not proven' verdict. The use of two different acquittal verdicts is a distinctive feature of Scots law and not typical of other systems. One justification offered for the not proven verdict is that it can be applied where a jury considers that an accused may be guilty but does not accept that there is adequate corroboration.19 As a result some might argue that removal of the requirement for corroboration would render the not proven verdict unnecessary. There is also an argument that has been advanced that, without the requirement for corroboration, the distinction between not proven and not guilty would become much harder to appreciate, running the risk of confusing jurors as to its use. These are largely technical legal arguments and little is known about how juries view the not proven verdict and whether they see it in these terms. The alternative view is that the not proven verdict provides additional protection over other systems in a context where there is no requirement for corroboration by offering the jury a verdict which accepts there is evidence against the accused but not enough to convict.

9.18 In 1994 the then Scottish Office consulted on the 3 verdict system, juries of 15 people and simple majority verdicts. Taking account of the differing views expressed and the relevant features of the jury system, the Scottish Office decided to retain all three elements.20

9.19 In 2008 the Scottish Government consulted on the size of juries and simple majority verdicts - The Modern Scottish Jury in Criminal Trials. The Scottish Government having considered responses brought forward legislation in respect of juries but decided not to alter the size of juries or simple majority verdicts at that time.

9.20 The Carloway Report's supplementary recommendation on corroboration, designed to ensure that there should be no requirement on a judge to warn the jury of any dangers perceived to arise purely as a consequence of the absence of corroboration, has attracted little public comment.

Related developments

9.21 The Scottish Law Commission's Report on Similar Fact Evidence and the Moorov doctrine was published on 23 May 2012. The Carloway Report discusses the relationship between Moorov and corroboration from para. 7.2.19.

9.22 The SLC's recommendation in relation to the use of previous convictions has the potential to increase the range of evidence available to the court in certain circumstances. For example, it may permit evidence to be led that shows a propensity by the accused towards a committing certain type of offence or that identifies certain patterns of past behaviour that may be relevant to the current case. The Government will carefully consider the interaction of the SLC's recommendations with the Carloway Report.

Scottish Government View

9.23 The Scottish Government agrees that the requirement for corroboration in criminal cases should be abolished. The rationale for the rule stems from another age, its usage has become confused and it can bar prosecutions that would in another legal system seem entirely appropriate.

9.24 Abolition is not expected to result in a substantial number of cases based upon uncorroborated evidence. As outlined by Lord Carloway, change is not being propounded in order to favour the prosecution of crime. Police and prosecutors will continue to seek the best evidence that can practically be made available in every criminal case. Judges and juries will be highly unlikely to convict on the basis of meagre evidence. The focus is upon modernising and remodelling the justice system. It is difficult to dispute Lord Carloway's assertion that criminal cases should be decided upon the basis of the overall quality of the evidence, without being distorted by the application of an outdated and overly technical set of rules.

9.25 The Government is not minded to revisit Lord Carloway's recommendation on removal of the requirement for corroboration or to remit this question to a further review. The focus of the Government is now upon deciding how to best achieve abolition and what, if any, additional measures require to be taken as a consequence. It is on that basis that the Government invites the views of those responding to this paper.

9.26 The question then becomes one of whether the wider system of protections in Scots law is sufficient to prevent miscarriages of justice in the absence of a requirement for corroboration. While we have listened carefully to the range of commentators who have advocated a need to change jury majorities and the like, we are persuaded by Lord Carloway's logic that this is not necessary at the current time. The protections for suspected and accused persons in Scotland following implementation of the Carloway reforms will continue to be substantial - access to legal advice, the right to silence, extensive rights of disclosure, the need for cases to be proved beyond reasonable doubt, the three verdict system and rights of appeal. In this context, we do not believe that the removal of the requirement of corroboration will result in a fundamental unbalancing of the system. Fundamentally, like Lord Carloway, we trust judges and juries to make judgments based on the quality of evidence before them.

9.27 While several contrary arguments have been advanced, to date limited hard evidence has been put forward in support of the potential risks that have been identified. This consultation provides the opportunity for those commentators and interests to provide any evidence that they consider makes these potential concerns real and significant rather than just theoretical.

Question 31

Lord Carloway concludes that the requirement for corroboration has no place in a modern legal system and should be abolished. Setting aside any question about whether this would require other changes to be made, do you agree with that conclusion?

Question 32

If the requirement for corroboration is removed, do you think additional changes should be made to the criminal justice system?

  • If you think additional changes should be made, what specific changes would you suggest and why? For example, if altering the size of jury majority required or verdicts what would a new system require or include?
  • What evidence do you have to support your position?