The not proven verdict and related reforms: consultation

This consultation seeks views on the three verdict system in Scottish criminal trials and if the not proven verdict were to be abolished, whether any accompanying reforms would be necessary to other aspects of the criminal justice system.

Part 5: The Corroboration Rule

The requirement for corroboration has been a unique feature of criminal law in Scotland for hundreds of years. The basic principle of the corroboration rule is that an accused cannot be convicted of a crime, unless the essential facts of the crime are able to be established by evidence from at least two independent sources. The essential facts are:

1. that the crime was committed; and

2. that the accused was the person who committed the crime.

Evidence can take many forms, including direct evidence such as that of an eyewitness, admissions made by the accused, and evidence of facts and circumstances (known as circumstantial evidence). At its most simple, corroborated evidence may come from two eyewitnesses who can both say they saw the crime being committed and can identify the accused as the perpetrator. Alternatively, one strong, clear source of evidence may be corroborated by evidence of facts and circumstances pointing to the guilt of the accused, such as a witness who saw the accused running from the scene of the crime, at the relevant time, holding a weapon that matches the relevant description.

At the other end of the scale, a corroborated case can come from entirely circumstantial evidence from two or more sources. Each fact or circumstance may, on its own, be of little significance but the strength of the case is based on their combination giving rise to an inference that the accused committed the crime. Only one witness need speak to each fact or circumstance.

A clear admission freely made by an accused is only one source of evidence and requires to be corroborated. The exception to that is where the admission contains “special knowledge”, which is knowledge which could only be known to the person who committed the crime, such as an accused confessing to murder and telling the police where the victim’s body has been concealed.

The significance of the corroboration rule

The rule requiring corroborative evidence is seen by some as a protection against miscarriages of justice in that it ensures that no person can be convicted of an offence solely on the basis of the testimony of a single witness.

The requirement for corroboration runs throughout the Scottish criminal justice system. For example:

(i) A prosecutor may not take prosecutorial action unless they believe there is sufficient evidence in law – i.e. corroborated evidence of the essential facts.

(ii) At the end of the Crown case, the case may be brought to an end by the judge, and the accused found not guilty, if the judge concludes that the evidence led by the Crown is not sufficient in law – i.e. if evidence of the crucial facts is not corroborated.

(iii) The judge is required to explain corroboration to the jury. Since July 2020 it has been agreed that jurors should be provided with certain materials in writing at the start of the trial. These set out amongst other things, the general directions which apply in every case as well as, if appropriate, specific directions which should also be provided in writing and read to the jury at the same time, depending on the circumstances (written directions on corroboration can be seen in Annex B).

(iv) An appeal may be taken on the ground that there was insufficient evidence in law (i.e. there was not corroborated evidence of the essential facts) to support a conviction.

(v) For these reasons, the investigation of a criminal case must be undertaken with the corroboration rule firmly in mind. Each essential fact must be capable of being proved by corroborated evidence. So, for example, a suspicious death will involve a two doctor post mortem, so that the cause of death can be corroborated; and expert reports (e.g. DNA, fingerprint analysis) will generally be produced jointly by two experts.

Corroboration in cases often committed in private such as sexual crimes

Corroborated evidence is more likely to exist in relation to some offences than others. For example, for crimes that are usually committed in private, the only potential evidence may be from the testimony of a complainer. This can be a particular barrier to obtaining corroboration for crimes such as domestic abuse, sexual crimes, and other abuse that may take place in a private or domestic setting such as abuse of older or otherwise vulnerable people. Therefore it has been argued that the practical effect of the requirement for corroboration can be to deny access to justice for victims of these types of crime.

The essential facts of the crime of rape[19] are: identification of the accused, penetration and lack of consent. The traditional approach in rape cases was to consider each of the essential facts separately in assessing the presence of corroborative evidence. This has been developed in recent case law, outlined in Annex C.

A number of rules have developed over time to broaden what can be considered to be corroborating evidence and which lessen the challenges set out above, in some cases. Of particular relevance to sexual offence cases are the following:

  • Distress: A series of cases has developed the rule that independent evidence of distress shown by the complainer which is attributable to the sexual assault can corroborate lack of consent. The rule was initially applied only in cases where the distress was shown a short time after the incident. However, this has developed to a position where what matters is whether the distress can be shown to have been caused by the sexual assault rather than the time interval being a determining factor.
  • The doctrine of mutual corroboration (also known as the Moorov doctrine): The evidence of single witnesses to different incidents may provide what is known as mutual corroboration in certain circumstances. For example, in the Moorov case itself where an employer carried out a series of sexual assaults against female staff, it wasn’t necessary for the complainers to have witnessed the assault on each other; each complainers’ testimony about what happened to them, was considered enough to corroborate the evidence of other complainers where the incidents were sufficiently similar in “time, character and circumstance” from which an overall course of criminal conduct could be inferred.

It is not necessary for the crimes charged to be the same. For example, the evidence of a rape complainer and a complainer of lesser sexual assault can be mutually corroborative if there are sufficient similarities, such as the accused using similar methods to meet complainers and gain their trust. It should be noted that the doctrine of mutual corroboration does not apply only to sexual assault cases.

Calls for reform of the corroboration rule

However, despite these developments some argue that the corroboration rule should be either reformed or removed entirely. That is why the Scottish Government is giving further consideration to the issue in this consultation.

There have been suggestions that the corroboration rule could be selectively removed for particular offences or aspects of offences, for example for sexual offences. However, this has been criticised as overly complex, lacking in principle, and creating a two-tier system.

Although this section refers to specific issues the corroboration rule can cause when prosecuting sexual crimes and other crimes committed in private, it is important to note that the rule applies to the majority of criminal cases.[20] This would include, for example, cases where a police officer is the only witness to the alleged offence.

Abolishing the rule in order to avoid issues for some sex offence cases might lead to problems in other types of cases. However, such issues are dealt with in other jurisdictions who do not have this rule.

Previous consideration of corroboration reform

The Carloway Review, published in 2011, found no evidence that corroboration protects against unsafe convictions and suggested that corroboration could be a barrier to justice by creating an additional obstacle to the prosecution of some offences, such as rape, where corroboration may be difficult to obtain. The report recommended the removal of the requirement for corroboration.

The Scottish Government listened closely to the discussion following the publication of this report and then carried out two further consultation exercises: first on the recommendations of the Carloway Review, and then - when it became clear that a majority of respondents supported keeping the corroboration rule - a further consultation on Additional Safeguards Following the Removal of the Requirement for Corroboration.

Following this engagement, the Scottish Government proposed abolishing the corroboration requirement in all criminal proceedings in the Criminal Justice (Scotland) Bill – introduced in 2013.

During the parliamentary consideration some of the main arguments raised for corroboration abolition were:

  • The practical impact on victims whose cases cannot be heard in court, even in some cases where there may be a reasonable prospect of conviction in another jurisdiction.
  • The principle that corroboration is outdated, watered down by recent case law and out of step with comparable justice systems.
  • The complexity that has built up around the corroboration requirement such that it is not well understood or easily explained.

Although there was some support for these points, particularly from organisations that support victims of crimes, there was strong opposition from a significant number of stakeholders. They were concerned that although other common law countries do not have a general corroboration rule, abolition may lead to a decrease in the quality of evidence and would not improve access to justice in a meaningful way for victims, particularly if cases were taken forward where there is not a realistic expectation of a significant increase in convictions.

Stakeholders argued that the case for abolition had paid insufficient attention to the importance of the corroboration rule in ensuring that the Scottish criminal justice system as a whole is properly balanced and gives due weight to the interests of those facing criminal allegations. Consequently there was a strong view that if the rule was to be abolished then additional provisions needed to be in put in place to protect against wrongful convictions.

In light of these concerns, Lord Bonomy was appointed to head an independent review to consider what additional safeguards might be necessary. Consideration of stage 2 amendments for the Criminal Justice (Scotland) Bill was postponed until after publication of the review’s recommendations.

On the day of the publication of Lord Bonomy’s report in April 2015, the former Cabinet Secretary for Justice, Michael Matheson MSP, announced that it had not been possible to build agreement around the reform. Therefore, although the Scottish Government still believed there to be a case for abolishing the requirement for corroboration, he now considered that the corroboration provisions (and related measures dealing with jury majorities) should be removed from the Bill.

Lord Bonomy’s review recommended a wide range of criminal justice reforms, indicating that some of these would be worthwhile improvements, independent of corroboration reform. The review group were unable to make any specific recommendations for the jury system due to a lack of research on the unique elements of Scottish juries (simple majority, jury size and three verdicts) so they recommended that research should be undertaken to better understand the dynamics of decision-making in Scotland’s jury system.

Recent developments in law

It is important to note that how the corroboration rule works in practice, and its effect has developed substantially since these previous parliamentary considerations. This has been especially relevant for sexual offence and domestic abuse cases. In recent years, the Appeal Court has taken a broad, pragmatic and holistic approach and developments have been made in areas including distress, penetration, and mutual corroboration, so that it is now far more possible, in relation to sexual offences, to establish sufficient corroborated evidence in law.

The law on “dockets” has also been developed by the Court, leading to changes in policy and practice surrounding how these are used. A docket is a type of legal document which is used in a criminal trial.[21] It allows prosecutors to lead evidence of behaviour which isn’t included in the charges against the accused person. The purpose of leading such evidence is that it may be capable of corroborating the charge(s) against the accused person.

Separately, in 2019, section 1 of the Domestic Abuse (Scotland) Act 2018 came into force and created a new statutory domestic abuse offence. This new offence can be committed when a person engages in a course of behaviour which is abusive. A course of behaviour involves behaviour on at least two occasions. It is not necessary for the prosecutor to lead evidence that corroborates behaviour that has occurred on each occasion that makes up the course of behaviour which is specified in the charge. It is the course of behaviour itself that constitutes the offence which has to be corroborated by two sources of evidence.

Further detail is included at Annex C.

Jury research and engagement

The background to the jury research is set out in the introduction to this consultation. Although the jury research did not specifically consider the corroboration rule, the mock jurors were given standard directions on the meaning of corroboration as if they were in a real trial. In general, jurors appeared to have fewer difficulties understanding the corroboration requirement than other legal issues such as the standard of proof. However, there were occasional incorrect comments in the mock juries’ discussions of the rape trial, suggesting that the doctor’s forensic evidence would have to unequivocally indicate rape before the jury could convict. Although these comments were made by individuals in the mock jury discussions that took place in the study, it is not possible to say whether they had any impact on the verdicts those mock juries eventually reached.

As well as considering the findings from the jury research, a series of subsequent engagement events provided an opportunity to hear participants’ views on related reforms such as corroboration.

Abolishing the corroboration rule was opposed by the substantial majority of those who participated in the engagement sessions, including legal professionals, officials from various public bodies giving their personal views, and academia. Even in groups who were open to other reforms such as moving to two verdicts, there was very limited support for this position and opposition was particularly strong amongst legal professionals. The small number who supported the abolition and/or reform of the corroboration rule – primarily, although not exclusively survivors - based this on a belief that it prevents strong cases with good quality evidence from getting to court, that the rule fails victims, that it is overly complex, hard to understand and not consistently applied and that it is hard to justify why Scotland alone, uniquely needs the corroboration rule.

The main reasons provided for keeping the corroboration rule were that it is a fundamental safeguard against wrongful conviction that the Scottish legal system is built on, and that its application has been significantly altered in recent years due to developments in case law.


As set out above, most of the participants in the engagement sessions did not feel that reform or abolition of the corroboration rule would be desirable, either as a standalone reform, or linked to a move to a two verdict system.

However, the importance of a holistic approach was repeatedly emphasised, so it was considered appropriate to seek stakeholders’ views on the corroboration rule alongside the other aspects of the jury system to facilitate this discussion of the whole system and its key safeguards.

Furthermore, as a government we understand the concerns with how the corroboration rule can affect access to justice for survivors of crimes committed in private. That was one of the main reasons why we previously tried to take forward corroboration reform and have now committed to giving it further consideration.


Having considered the views expressed throughout previous considerations of the corroboration rule, developments in case law, the evidence from the recent jury research and views gathered at the subsequent engagement sessions, the Scottish Government is seeking views on the following questions.

These questions focus on corroboration. There are specific questions on not proven in part 2, jury size in part 3 and jury majority in part 4.

Question 11: Which of the following best reflects your view on what should happen with the corroboration rule in the following situations?

a) If Scotland remains a three verdict system and keeps the simple majority:

  • Scotland should abolish the corroboration rule
  • Scotland should reform the corroboration rule
  • Scotland should keep the corroboration rule as it is currently Please give reasons for your answer:

b) If Scotland changes to a two verdict system and keeps the simple majority:

  • Scotland should abolish the corroboration rule
  • Scotland should reform the corroboration rule
  • Scotland should keep the corroboration rule as it is currently Please give reasons for your answer:

c) If Scotland changes to a two verdict system and increases the jury majority:

  • Scotland should abolish the corroboration rule
  • Scotland should reform the corroboration rule
  • Scotland should keep the corroboration rule as it is currently Please give reasons for your answer:

Question 12: If the corroboration rule was to be reformed, rather than abolished, what changes do you feel would be necessary?

Question 13: Do you feel further safeguards against wrongful conviction should be in place before any reform or abolition of the corroboration rule? Yes/No

Please give reasons for your answer, including what other safeguards you believe would be appropriate and why:

Question 14: If the corroboration rule was kept or reformed, what else could be done to help people, including those involved in the justice system and the general public, to understand it better?



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