The Understanding Requirement in Testimony of the Mentally Disabled (R. v. D.A.I.)

In the post-Charter era, we’ve become increasingly aware of vulnerable populations and the need to address societal imbalances in power. But as I highlighted last month, the mentally ill still continue to face unnecessary barriers that often prevents full participation in society.

The Supreme Court of Canada released a judgment on Friday which could help combat sexual abuse against the mentally ill. The mentally disabled are frequent targets for sexual assaults given their perceived inability to relate the incidents to others. Some estimate this risk factor may be as high as four to ten times higher than the general population.


The complainant in R. v. D.A.I., 2012 SCC 5, was a woman who was 26 at the time of the decision. She alleged she was sexually assaulted numerous times by her mother’s partner over the course of four years when she was 19 years of age, but was estimated to have the mental capacity of a three to six-year-old. The majority of the court allowed the appeal, set aside the acquittal, and directed a new trial with a requirement that the complainant only need to “promise” to tell the truth rather than demonstrate an understanding of the duty to tell the truth.


The accused had questioned the complainant’s testimonial capacity at trial, and a voire dire was conducted. Although she could understand the difference between telling the truth and lies, she could not respond to more philosophical questions on the nature of truth and morality. The trial judge stated,

Having questioned [K.B.] at length I am fully satisfied that [K.B.] has not satisfied the prerequisite that she understands the duty to speak the truth. She cannot communicate what truth involves or what a lie involves, or what consequences result from truth or lies, and in such circumstances, quite independent of Doctor Kunjukrishnan, I am not satisfied that she can be permitted to testify under a promise to tell the truth.

. . .

As I say this is a criminal trial involving criminal charges and while every effort should be brought to bear to accommodate witnesses with disabilities, at the end of the day the Court has an obligation to ensure that evidence that is going to be used in an attempt to convict an individual must meet the requirements of the law, and in this case unfortunately [K.B.] cannot be permitted to give evidence.

The trial judge based this determination on the procedural safeguards against wrongful convictions in s. 16(3) of the Canada Evidence Act,

Witness whose capacity is in question

16. (1) If a proposed witness is a person of fourteen years of age or older whose mental capacity is challenged, the court shall, before permitting the person to give evidence, conduct an inquiry to determine

(a) whether the person understands the nature of an oath or a solemn affirmation; and

(b) whether the person is able to communicate the evidence.

Testimony on promise to tell truth

(3) A person referred to in subsection (1) who does not understand the nature of an oath or a solemn affirmation but is able to communicate the evidence may, notwithstanding any provision of any Act requiring an oath or a solemn affirmation, testify on promising to tell the truth.

Inability to testify

(4) A person referred to in subsection (1) who neither understands the nature of an oath or a solemn affirmation nor is able to communicate the evidence shall not testify.

[emphasis added]

Majority Decision

Chief Justice McLachlin, for the majority, began by clarifying three concepts that she stated were often confused:

(1) the witness’s competence to testify;
(2) the admissibility of his or her evidence; and
(3) the weight of the witness’ testimony.

Although evidentiary rules of all share the purpose of ensuring a fair trial based on solid evidence, they each play a different role in achieving that goal by ensuring that a guilty verdict is only based on accurate and credible evidence presented at a fair trial.

A finding of competence will not guarantee that the evidence will be admissible or accepted by the court. Witnesses are presumed the basic capacity to testify, but a party may challenge competence. This threshold of competence is simply a basic capacity to communicate evidence to court. Absent any rules against admissibility, the trier of fact must still assess demeanour, internal consistency, and consistency with other evidence, before determining the weight afforded to any testimony.

McLachin CJ stated that the complainant did not meet the first requirement for competence under s. 16(1)(a) of the Act, and the proper inquiry was therefore under s. 16(3). She indicated that the plain reading of the section suggests that a person is competent to testify if they respond to the affirmative to an inquiry of promising to tell the truth. She rejected the respondent’s submission that this question must be supplemented by a determination of whether they understand the nature of such a promise.

She cited the court in Rizzo Shoes Ltd. (Re) to conclude that there is no further requirement under the Act,

21 Although much has been written about the interpretation of legislation (see, e.g., Ruth Sullivan, Statutory Interpretation (1997); Ruth Sullivan, Driedger on the Construction of Statutes (3rd ed. 1994) (hereinafter “Construction of Statutes”); Pierre-André Côté, The Interpretation of Legislation in Canada (2nd ed. 1991)), Elmer Driedger in Construction of Statutes (2nd ed. 1983) best encapsulates the approach upon which I prefer to rely. He recognizes that statutory interpretation cannot be founded on the wording of the legislation alone. At p. 87 he states:

 Today there is only one principle or approach, namely, the words of an Act are to be read in their entire context and in their grammatical and ordinary sense harmoniously with the scheme of the Act, the object of the Act, and the intention of Parliament.

 Recent cases which have cited the above passage with approval include: R. v. Hydro-Québec, [1997] 3 S.C.R. 213**Royal Bank of Canada v. Sparrow Electric Corp., [1997] 1 S.C.R. 411; Verdun v. Toronto-Dominion Bank, [1996] 3 S.C.R. 550; Friesen v. Canada, [1995] 3 S.C.R. 103.
[emphasis added]

The respondent’s submission of a further requirement beyond an ability to requirement and a promise to tell the truth was rejected for the following reasons:

  1. This interpretation would go beyond the words used by Parliament on a plain words reading. Although ambiguity may require reference to external factors, there is no ambiguity in the section.
  2. The history of the section indicates that Parliament introduced these amendments in 1987 to alter the common law rule where only witnesses under oath could testify, in order to remove barriers preventing the mentally disabled from testifying. The legislative history demonstrates that the wording was altered to specifically avoid the interpretation requiring further demonstration by a witness.
  3. The respondent’s submission was internally illogical, because s. 16(3) would add little to s. 16(1) if the witness is required to demonstrate an understanding of the obligation to tell the truth. (Often referred to in statutory interpretation as the Rule Against Absurdity)
  4. The wording in s. 16(4) only requires the ability to communicate evidence as the only requirement under s. 16(3), and additional qualitative requirements would flout the utility of s. 16(4).
  5. The conditions under s. 16(3) mirror the requirements under ss. 16.1(3), (5) and (6) for the competence of children, and consistency of Parliament should be assumed absent any indication to the contrary.

McLachlin CJ then addressed whether a promise itself is sufficient, or whether it would be an empty gesture,

[36] Promising is an act aimed at bringing home to the witness the seriousness of the situation and the importance of being careful and correct. The promise thus serves a practical, prophylactic purpose. A witness who is able to communicate the evidence, as required by s. 16(3), is necessarily able to relate events. This in turn implies an understanding of what really happened — i.e. the truth — as opposed to fantasy. When such a witness promises to tell the truth, this reinforces the seriousness of the occasion and the need to do so. In dealing with the evidence of children in s. 16.1, Parliament held that a promise to tell the truth was all that is required of a child capable of responding to questions. Parliament did not think a child’s promise, without more, is an empty gesture. Why should it be otherwise for an adult with the mental ability of a child?

She then dealt with the fact that Parliament did not extend s. 16.1(7) to adults with mental disabilities in 2005, which would lead to a presumption that the previous Act did not exclude a requirement of understanding. The current section, which focuses on children and does not apply to the mentally disabled, states,

Person under fourteen years of age

16.1 (1) A person under fourteen years of age is presumed to have the capacity to testify.

Understanding of promise

(7) No proposed witness under fourteen years of age shall be asked any questions regarding their understanding of the nature of the promise to tell the truth for the purpose of determining whether their evidence shall be received by the court.
[emphasis added]

Parliament made these changes based on developments in case law such as the Court of Appeal in R v. Khan, and the Brief on Bill C-2: Recognizing the Capacities & Needs of Children as Witnesses in Canada’s Criminal Justice System, Child Witness Project, referred to by the court as the “Bala Report.” (You can read a subsequent paper by Prof. Bala discussing some of these issues in the International Journal of Children’s Rights).

McLachlin CJ also referred to the parliamentary works on the bill that the amendments were not intended to modify law, but to confirm the existing formal requirement of a promise alone,

Mr. Joe Comartin (Windsor—Tecumseh, NDP): Professor Bala, to start, I read your material in the paper around the changes you want to proposed subsection 16.1(7), but I don’t understand, quite frankly, how you would change it. Proposed subsection 16.1(6) provides, as you’re promoting strongly, that no oath be issued, that they simply be required to promise to tell the truth.

So I don’t know exactly how you want (7) amended, from its current proposal.

Prof. Nicholas Bala: The concern I have about proposed subsection 16.1(7) is that it says no child shall be asked any questions regarding their understanding of the nature “of the promise” for the purpose of determining whether their evidence shall be received by the court, and I would submit to you that it should be “of the promise to tell the truth”.

It’s a relatively small change, but again, the concern I have arises out of the fact that the present legislation has been interpreted very narrowly by judges. When you actually go back through the transcripts—I was actually a witness in 1988, when the provisions came into effect—I think it was thought by people, well, we don’t have to be very explicit here, because the judges will get this right.

Obviously, on many issues we do have to trust our judiciary, but on certain issues I think it’s important to give them as much direction as possible. My concern is that some judge might read this—and we have quite a lot of case law about this—and say, okay, I can’t ask you about your understanding of the nature of the promise, but what about asking you questions about truth-telling? Parliament specifically said in subsection 16.1(6) that you’ll be required to promise to tell the truth. We can’t ask about the nature of the promise, but can we ask you about “truth” and “lie”?

Some judges will continue to interpret it that way. In some ways, it’s a very small amendment, but I assume it’s consistent with your actual intent. My concern, as I say, has been based on how some of these previous provisions have been interpreted.

This was confirmed by proceedings before the Standing Senate Committee on Legal and Constitutional Affairs,

The other part concerns the amendments to the Canada Evidence Act with respect to children. Under the current law, the Canada Evidence Act treats children under 14 in the same way as it treats other people whose mental capacity is challenged. There is a current section 16 that requires the judge to conduct a two-part inquiry whether they are dealing with a person who has some mental disabilities or whether they are dealing with a child under 14. The two-part inquiry requires the judge to first determine, in the case of a child, whether the child understands the nature of an oath or the nature of a solemn affirmation and, second, to determine if the child is able to communicate the evidence. These amendments were made in 1988 with the purpose of trying to more readily permit children’s evidence to be received. However, as the cases have interpreted this provision, we have not seen that ready acceptance of children’s evidence.

If these two criteria are met, the child gives evidence under an oath or an affirmation. However, if the child does not understand the nature of the oath or the affirmation but has the ability to communicate the evidence, the evidence is received on a promise to tell the truth. That is the current law. While it may appear quite sensible on its face, the interpretations and practise of these provisions do not reflect Parliament’s intention in amending the Evidence in an effort to permit children’s evidence to be admitted more readily.

As interpreted by the courts, section 16 requires that before the child is permitted to testify, the child be subjected to an inquiry as to his or her understanding of the obligation to tell the truth, the concept of a promise, and an ability to communicate. While the Supreme Court of Canada has commented on the absurdity of questioning children about their understanding of the religious consequences of oaths in getting past that first hurdle of whether or not they understand an oath or affirmation, those questions about religious beliefs continue to prevail, although adults are never asked the same questions.

Parliament’s introduction of this section arose out of concern that the judiciary was interpreting the Act as requiring this type of questioning instead of a simple promise, and not because this amendment was removing the understanding requirement. She cited the appropriate provision of the Interpretation Act,

Repeal does not imply enactment was in force

45. (1) The repeal of an enactment in whole or in part shall not be deemed to be or to involve a declaration that the enactment was previously in force or was considered by Parliament or other body or person by whom the enactment was enacted to have been previously in force.

Amendment does not imply change in law

(2) The amendment of an enactment shall not be deemed to be or to involve a declaration that the law under that enactment was or was considered by Parliament or other body or person by whom the enactment was enacted to have been different from the law as it is under the enactment as amended.

Repeal does not declare previous law

(3) The repeal or amendment of an enactment in whole or in part shall not be deemed to be or to involve any declaration as to the previous state of the law.

Judicial construction not adopted

(4) A re-enactment, revision, consolidation or amendment of an enactment shall not be deemed to be or to involve an adoption of the construction that has by judicial decision or otherwise been placed on the language used in the enactment or on similar language.
[emphasis added]

Finally, McLachlin CJ discussed some policy considerations which are worth quoting in full,

[66] The first policy consideration is self-evident and requires little amplification. Those with mental disabilities are easy prey for sexual abusers. In the past, mentally challenged victims of sexual offences have been frequently precluded from testifying, not on the ground that they could not relate what happened, but on the ground that they lacked the capacity to articulate in abstract terms the difference between the truth and a lie and the nature of the obligation imposed by promising to tell the truth. As discussed earlier, such witnesses may well be capable of telling the truth and in fact understanding that when they do promise, they should tell the truth. To reject this evidence on the ground that they cannot explain the nature of the obligation to tell the truth in philosophical terms that even those possessed of normal intelligence may find challenging is to exclude reliable and relevant evidence and make it impossible to bring to justice those charged with crimes against the mentally disabled.

[67] The inability to prosecute such crimes and see justice done, whatever the outcome, may be devastating to the family of the alleged victim, and to the victim herself. But the harm does not stop there. To set the bar too high for the testimonial competence of adults with mental disabilities is to permit violators to sexually abuse them with near impunity. It is to jeopardize one of the fundamental desiderata of the rule of law: that the law be enforceable. It is also to effectively immunize an entire category of offenders from criminal responsibility for their acts and to further marginalize the already vulnerable victims of sexual predators. Without a realistic prospect of prosecution, they become fair game for those inclined to abuse.

[68] What then of the policy considerations on the other side of the equation? Here again, the starting point is clear. The Canadian Charter of Rights and Freedoms guarantees a fair trial to everyone charged with a crime. This right cannot be abridged; an unfair trial can never be condoned.

[69] It is neither necessary nor wise to enter on the vast subject of what constitutes a fair trial. One searches in vain for exhaustive definitions in the jurisprudence. Rather, the approach taken in the jurisprudence is to ask whether particular rules or occurrences render a trial unfair. It is from that perspective that we must approach this issue in this case.

[70] The question is this: does allowing an adult witness with mental disabilities to testify when the witness can communicate the evidence and promises to tell the truth render a trial unfair? In my view, the answer to this question is no.

[71] The common law, upon which our current rules of evidence are founded, recognized a variety of rules governing the capacity to testify in different circumstances. The golden thread uniting these varying and different rules is the principle that the evidence must meet a minimal threshold or reliability as a condition of being heard by a judge or jury. Generally speaking, this threshold of reliability is met by establishing that the witness has the capacity to understand and answer the questions put to her, and by bringing home to the witness the need to tell the truth by securing an oath, affirmation or promise. There is no guarantee that any witness —even those of normal intelligence who can take the oath or affirm — will in fact tell the truth, all the truth, or nothing but the truth. What the trial process seeks is merely a basic indication of reliability.

[72] Many cases, including Khan, have warned against setting the threshold for the testimonial competence too high for adults with mental disabilities: R. v. Caron(1994), 72 O.A.C. 287; FarleyParrott. This reflects the fact that such witnesses may be capable of giving useful, relevant and reliable evidence. It also reflects the fact that allowing the witness to testify is only the first step in the process. The witness’s evidence will be tested by cross-examination. The trier of fact will observe the witness’s demeanour and the way she answers the questions. The result may be that the trier of fact does not accept the witness’s evidence, accepts only part of her evidence, or reduces the weight accorded to her evidence. This is a task that judges and juries perform routinely in a myriad of cases involving witnesses of unchallenged as well as challenged mental ability.

[73] The requirement that the witness be able to communicate the evidence and promise to tell the truth satisfies the low threshold for competence in cases such as this. Once the witness is allowed to testify, the ultimate protection of the accused’s right to a fair trial lies in the rules governing admissibility of evidence and in the judge or jury’s duty to carefully assess and weigh the evidence presented. Together, these additional safeguards offer ample protection against the risk of wrongful conviction.


The dissent, led by Justice Binnie, with LeBel and Fish JJ. concurring, emphasized the need for a“conception of any moral obligation to say what is ‘right’.” This is necessarily in order to conduct a meaningful cross-examination, without which would create unfair prejudice for the accused. The trial judge’s reasons for excluding the complainant’s testimony included concerns over hearsay and out-of-court statements, and the inability to respond to relatively simple questions around the allegations that would allow the testimony to be challenged for credibility. He stated that the understanding of a promise was required to protect the legitimate interest of the accused to a fair trial,

[105] …If such a witness is so disabled as not to understand “the seriousness of the situation and the importance of being careful and correct”, there is no prophylactic effect, and the fair trial interests of the accused are unfairly prejudiced.

Binnie J interpreted R v. Khan as not requiring an abstract inquiry into the nature of the promise, and preferred the test used in Khan as adopted from R v. Bannerman,

To satisfy the less stringent standards applicable to unsworn evidence, the child need only understand the duty to speak the truth in terms of ordinary everyday social conduct. This can be demonstrated through a simple line of questioning directed to whether the child understands the difference between the truth and a lie, knows that it is wrong to lie, understands the necessity to tell the truth, and promises to do so. It is to be borne in mind that under s. 16(2) the child’s unsworn evidence must be corroborated by some other material evidence. Any frailties that may be inherent in the child’s testimony go to the weight to be given the testimony rather than its admissibility.

Binnie J questioned the lack of ambiguity of the expression “promising to tell the truth” in s. 16 as expressed by the majority by citing McLachlin J. in R. v. Marquard,

The phrase “communicate the evidence” indicates more than mere verbal ability. The reference to “the evidence” indicates the ability to testify about the matters before the court. It is necessary to explore in a general way whether the witness is capable of perceiving events, remembering events and communicating events to the court. If satisfied that this is the case, the judge may then receive the child’s evidence under s. 16(3), after the child has promised to tell the truth. It is not necessary to determine in advance that the child perceived and recollects the very events at issue in the trial, as a condition of ruling that his or her evidence be received. That is not required of adult witnesses, and should not be required for children.
[emphasis added]

The trial judge should be able to ascertain whether a witness has more than just mere verbal ability, and determine if they can tell the difference between truth and fiction and the importance maintaining consistent testimony. He also disagreed over the legislative intent of the s. 16 history, citing the House of Commons, Minutes of Proceedings and Evidence of the Legislative Committee on Bill C-15, No. 2, 2nd Session, 33rd Parl., December 4, 1986, to highlight that nothing in the 1987 amendments suggests a mere verbal ability would be sufficient,

[The Hon. Mary] Collins: Yes. However, if we leave in the “sufficient intelligence”, and with the interpretation that has been given, I still feel that is going to be a potential barrier.

Mr. Pink: It may be that the committee is going to have to decide on words other than “sufficient intelligence”. What is the purpose of the query in the first place? Does it not really boil down to determining truth or falsehood? Is that not what it is all about?

[The Hon. Mary] Collins: I would think so. Yes. So if the child understands the difference between telling the truth and lying, that would seem to me to be all you would really need to find out.

Mr. Pink: I agree.

[The Hon. Mary] Collins: Thank you.
[Emphasis added by the court; p. 27.]

Justice Binnie agreed that the legislative changes arose out of the Bala Report, but pointed out that there was no research before Parliament for adults with mental disabilities. He referred to the s. 16.1(7) amendment of 2005 as the “don’t ask” rule, and stated that the majority was reading in the “don’t ask” rule into s. 16(3) for the mentally disabled. This robbed the section of its ordinary meaning of “promising to tell the truth.” Even the Crown agreed there are obvious distinctions between the test for adults with limited mental capacity under s. 16 and children under 14 years of age,

[128] …In my view, the difference is that a six-year-old with the mental capacity of a six-year-old does not suffer from a mental disability. The fact that psychiatrists speak of persons with mental disabilities calibrated in terms of mental ages is a useful way of describing the relative extent and severity of a person’s disability, but it does not mean that a 22-year-old woman with a severe mental disability is on the same footing as a six-year-old child with no mental disability whatsoever, and of course the empirical evidence before Parliament in 2005 did not suggest otherwise.

McLachlin CJ’s response at paras. 49-51 to the dissent’s argument was that it assumes a “don’t ask” rule was imported into the section of the Act. She also claimed the dissent’s argument was inconsistent, by claiming the equivalent vulnerabilities of children and mentally disabled was at issue, while still relying on the judicial holding for children in Khan and applying it to mentally disabled adults.

Justice Binnie also questioned McLachlin CJ’s application of the Interpretation Act, citing The Interpretation of Legislation in Canada,

The provisions [s. 45] do not, for example, present interpreting the act of amendment as an expression of the legislature’s opinion; they simply eliminate an a priori presumption (“shall not be deemed”). The context, or even the formulation (in the form of a preamble, for example), of an amendment is quite capable of marking a clear desire to change the state of the law.

Citing the dangers of hearsay, the inability to inquire into the witness’ perception, memory and credibility, Justice Binnie would have dismissed the appeal. He stated,

[145] Much of the dispute in this case turned on the significance of K.B.’s “I don’t know” answers. Clearly, it was an important advantage for the trial judge to watch the questions and answers unfold and to assess whether K.B. was actually able to “compute” her responses to what she was being asked ― a condition precedent, surely, to any ability to test her evidence by cross-examination. The trial judge observed K.B.’s demeanour as she struggled with the attempted dialogue. The trial judge was responsible for protecting the fair trial interests of the accused, as well as society’s interest in the prosecution of crimes. The inability of K.B. to deal with simple questions would mean that her evidence — however erroneous it might be, and however much (to pick up on her teacher’s observation) it might be the product of K.B’s wishful thinking — would be effectively immune to challenge by the defence, thereby prejudicing the interest of society as well as the accused in a fair trial.



  1. Omar, this is a well-written and timely entry which is similar to a case I attended (briefly), this summer, at London’s Old Baily. The case involved a mentally disabled woman, in her early 20’s, with a cognitive/social/emotional clinical age estimated to be equivalent to that of an 8 year old. She met her alleged rapist at a neighborhood convenience store while undertaking an errand for her Aunt(custodian). According to testimony, this was the first time the Aunt had allowed the victim to go to the store, during the day, unescorted. The challenge raised at trial was around consent (validity) and the standard of knowledge which would allow this woman to safeguard her own interests since she had no sexual experience and limited sexual education. Considerable expert testimony was directed at the markers of capacity to consent. In this case, there was physical/medical evidence confirming sexual intercourse had occurred.

    It would have been most interested to hear how this judge would have dealt with the issue of “promising to tell the truth” given the extent and severity of this woman’s mental disability.

  2. Thanks Diane.

    I was recently able to obtain Prof. Bala’s submissions from him directly, and I have his permission to distribute it here for those interested.

  3. After reading Prof. Bala’s brief on Bill C-2 and learning about his research findings, on the Child Witness Project, I was struck by the scope and significance of his work and its direct application to the above case. Am I correct in saying that to be legally competent to testify, this woman, has demonstrated the capacity (reasonable statement) of what was seen, felt or heard (has the ability to relate a series of events). In Justice Binnie’s interpretation (simplified) would this be her perception, memory and credibility? That the reliability (“truth vs falsehood”)of her observations, recollections and communication is a matter for the judge and/or jury thereby, preserving the accused rights to a fair trial and the victim’s rights to be fairly and justly heard.

    Truthfully, I hope you will continue to cover how the court deals with the relationship between competency, capacity, and reliability in ensuring the mentally disabled have a voice in our courts.