Witnesses and testimony in a criminal trial

Overview

A witness brings information to the court through an account that the parties can examine. Several questions precede the court's decision to believe that account: whether the person can testify, whether attendance can be compelled, how communication will occur, and whether the proposed answers are legally admissible. A person may be a competent witness yet have no admissible basis for a particular assertion.

This lesson addresses Canadian criminal trials, including trials in Quebec. The Canada Evidence Act and Criminal Code provide specific rules alongside common-law principles. The accused has particular protections, while children, people with disabilities and other witnesses may require arrangements that permit meaningful participation. Accommodating communication does not decide whether the account is accurate.

The useful preparation is witness-specific. Identify what the person personally perceived, what comes from another source, what records may assist, and what procedural orders are necessary. Then distinguish the admission question from the strength of the resulting evidence. A clear account can remain mistaken, and a hesitant account can remain accurate.

Learning Objectives

• Distinguish competence, compellability and the admissibility of particular answers.
• Apply the rules for questioning, memory and prior statements without treating counsel's suggestions as evidence.
• Explain the role of testimonial aids and the separate screening of expert opinion.

Determine who can and must testify

Capacity and the undertaking to tell the truth

Competence (habileté à témoigner) concerns the witness's capacity, rather than whether the court will accept the account. Under Canada Evidence Act s. 3, an interest in the outcome or a criminal history does not itself make a person incompetent. A solemn affirmation has the same evidentiary effect as an oath under s. 14. Choosing one form rather than the other supplies no reason to discount the testimony.

For a proposed witness aged fourteen or older whose mental capacity is challenged, s. 16 requires an inquiry before testimony into understanding an oath or affirmation and ability to communicate the evidence. The challenger first bears the burden of showing an issue concerning capacity to testify under oath or affirmation. A person who meets both requirements testifies under oath or affirmation. A person able to communicate who does not understand the oath or affirmation may testify on promising to tell the truth. The court cannot test that person's understanding of the promise as a condition of receiving the evidence.

A person under fourteen is presumed capable under s. 16.1. The child does not take an oath or affirmation; the court requires a promise to tell the truth. The operative capacity concerns understanding and responding to questions. A challenger must establish that an issue exists before the court conducts the prescribed inquiry. Questions testing the child's understanding of the nature of the promise are prohibited for this purpose. Evidence properly received has the same effect as evidence under oath.

These rules require attention to actual communication abilities. Difficulty with adult vocabulary or a disability label does not alone resolve capacity. Canada Evidence Act s. 6 permits suitable communication means where a physical disability creates communication difficulty, or where a witness with a mental disability has capacity under s. 16 but difficulty communicating. The court may inquire into the means' necessity and reliability. Separately, Charter s. 14 protects interpreter assistance for a party or witness who cannot understand or speak the proceeding's language, or who is deaf. Criminal Code s. 659 abolishes the mandatory jury warning about convicting on a child's evidence; age alone does not require that warning.

Compulsion and protected answers

Compellability (contraignabilité) raises a different question. The accused is competent to testify for the defence, but Charter s. 11(c) protects against being compelled as a witness in proceedings against that person concerning the offence. This protection must not be confused with a general right of every witness to refuse potentially incriminating questions. The protections for compelled testimony require their own analysis, addressed in statements and self-incrimination.

Marriage no longer makes a person incompetent or uncompellable for the prosecution merely because the accused is their spouse: Canada Evidence Act s. 4(2). Section 4(3) separately protects against compulsion to disclose communications made by a spouse during marriage. The distinction matters: a question about something observed is not necessarily a question about a protected communication. See privilege and confidentiality before assuming that attendance opens every subject to examination.

A subpoena under Criminal Code ss. 698–700 secures attendance where the person is likely to give material evidence. Its terms can require relevant things to be brought to court. The witness must attend and remain unless excused by the presiding judicial officer. Bringing records does not authorize unrestricted defence inspection, remove privilege or establish admissibility. Protected-record production requires the applicable process explained in disclosure and third-party records.

A witness should seek excusal rather than disregard the subpoena. Section 705 permits an arrest warrant for failure to attend or remain when proper service and the likelihood of material evidence are established. Failure to attend or remain without lawful excuse can also constitute contempt under s. 708. Those are separate judicial decisions, not automatic consequences imposed by the party calling the witness.

Arrange testimony so it can be heard and tested

Apply the correct aid and entitlement

A testimonial aid can reduce barriers without changing the prosecution's burden. Criminal Code s. 486.1 governs support persons and support animals; s. 486.2 governs testimony outside the courtroom or behind a screen or other device preventing the witness from seeing the accused. These are distinct orders with their own conditions. An application should identify the witness's category and the arrangement requested.

Under the current provisions, witnesses under eighteen and the specified witnesses with disabilities receive the relevant order on application unless it would interfere with the proper administration of justice. The disability wording differs between the two sections: for remote or screened testimony, the person must be able to communicate evidence but may have difficulty because of the disability. Section 486.1 does not impose that same communication-difficulty condition for a support person or animal.

The same presumptive routes also cover a victim witness in proceedings concerning a sexual offence or an offence committed for a sexual purpose, an offence related to criminal harassment or trafficking in persons, or an offence committed against the accused's intimate partner. The prosecutor or witness may apply. Other witnesses may seek discretionary orders based on facilitating a full and candid account or the proper administration of justice. Relevant factors include the relationship with the accused, intimidation and security concerns, the nature of the offence and participation in the justice system.

These expanded provisions came into force on July 18, 2026; the Protecting Victims Act, s. 102, makes the amended ss. 486.1–486.3 applicable to proceedings already ongoing. Their application is therefore not governed by the charge-date cutoff applicable to other reforms in that Act. Where a presumptive application has not been made, the judge must inquire whether the prosecutor took reasonable steps to inform the witness of the option. A refusal requires written reasons in the record.

An order for testimony outside court must preserve the arrangements in s. 486.2(5): the accused, judge and jury can watch through the specified technology, and the accused can communicate with counsel. The provisions prohibit an adverse inference from making or not making the order. Support should enable the witness's own account. Another witness cannot serve as support person unless the proper administration of justice requires it; the court may prohibit communication during testimony. Separate rules govern courtroom closure, identity protection and publication bans.

Separate personal confrontation from effective questioning

Section 486.3 governs an accused's personal cross-examination. For a witness under eighteen, and for victim witnesses in the specified offence categories, the court must on application prevent personal questioning unless the proper administration of justice requires it. Where the order is made, the court appoints counsel to conduct the cross-examination. Other witnesses have the distinct discretionary route under subsection (3).

The resulting arrangement preserves questioning through counsel. It does not establish the truth of the witness's account or bar legitimate challenges to perception, memory or inconsistencies. The section likewise requires inquiry about notice of the application option in the specified categories, written reasons for refusing an order, and no adverse inference from appointment or non-appointment.

Video-recorded testimony has a separate route. Under s. 715.1, the witness must have been under eighteen when the alleged offence occurred; a video made within a reasonable time after that offence, describing the acts complained of, is admissible when the witness adopts its contents while testifying, unless admission would interfere with the proper administration of justice. Section 715.2 supplies a corresponding route, without an age limit, for a witness able to communicate evidence but who may have difficulty doing so because of a mental or physical disability. Both sections allow the court to prohibit other uses of the video. They do not admit every police interview or eliminate the witness's participation.

Protect identity through the correct order

Section 486.31 permits an order withholding identifying information within the proceeding on the prosecutor's or witness's application. The judge must assess the proper administration of justice, including a fair and public hearing, safety, effective alternatives and the order's effects. A screen does not itself confer anonymity. No adverse inference follows from granting or withholding the identity order.

A publication ban instead restricts dissemination. For the offences listed in s. 486.4(1), the judge must inform victims and witnesses under eighteen of their application right as soon as feasible and grant a victim's, prosecutor's or such a witness's application. Subsections (2.1)–(2.2) separately protect victims under eighteen in other offences. In proceedings concerning child sexual abuse and exploitation material, s. 486.4(3) mandates an order protecting witnesses under eighteen and persons represented in that material.

When the prosecutor applies, the court must inquire about the protected person's wishes. As soon as feasible after the order, the prosecutor must report having informed that person of the order, determined their wishes and explained the right to seek variation or revocation. The judge also has a notification duty. Subsections (4)–(5) preserve specified disclosures, including one's own information without intentionally or recklessly revealing another protected person's identity or identifying particulars, and a victim's or witness's disclosures without a purpose of informing the public. Check the actual order and statutory exception before dissemination. These publication provisions have their own scope; the July 2026 testimonial-aid transition does not replace them.

Worked example: capacity and a screen for a child

Factual Scenario

In this hypothetical, twelve-year-old Sam is to testify in October 2026 about damage to a community workshop. Sam answers ordinary questions about what was seen but becomes confused by long questions containing several propositions. Sam asks to testify behind a screen. The defence objects that difficulty defining a promise proves incapacity and that a screen would improperly endorse the account. Assume the proceeding is governed by the Criminal Code and no concrete interference with the proper administration of justice is established.

Elicit and challenge an account fairly

The sequence of questioning

Examination-in-chief ordinarily develops the witness's own account through non-leading questions on disputed matters. A leading question can suggest the desired answer or assume a disputed fact, obscuring whether the witness remembers it. R. v. E.M.W., 2011 SCC 31, para. 9, distinguishes such questions from offering alternatives without suggesting an answer. The prohibition is not absolute: introductory, undisputed or otherwise permitted matters can justify a different approach. The court controls the questioning in context.

Cross-examination permits the opposing party to test the account and obtain helpful facts. Leading questions are generally permitted, but harassment, misrepresentation and prohibited evidentiary uses remain impermissible. Re-examination addresses matters arising from cross-examination; it is not an unrestricted opportunity to add a forgotten part of the original case. If genuinely new material requires further questioning, the court controls fairness and any opportunity for the opposing party to respond.

In R. v. Lyttle, 2004 SCC 5, paras. 41–52, the Supreme Court protects broad cross-examination based on a good-faith foundation. Counsel need not possess independent admissible proof of every factual suggestion. Information supporting the question can be incomplete, provided the hypothesis is honestly advanced on a proper basis rather than recklessly or deceptively. The judge may inquire into that basis where necessary.

The question itself proves nothing. If counsel suggests that a witness was distracted and the witness denies it, the suggestion does not become evidence of distraction. A final argument must distinguish the witness's answers, other admissible evidence and counsel's unaccepted proposition. Good-faith permission to ask does not guarantee permission to introduce extrinsic evidence on every collateral dispute.

Fairness also generally requires putting the substance of an intended contradiction to the witness so that an explanation can be offered. Lyttle, paras. 64–65, explains this notice principle and its flexible application according to the circumstances. Failure does not carry one automatic consequence in every trial. The court considers the actual unfairness and the appropriate response.

Keep memory and prior statements separate

Refreshing memory may occur through notes or another stimulus. The evidentiary point is the witness's revived recollection. In R. v. Fliss, 2002 SCC 16, paras. 43–46, the Court distinguishes that recollection from reading material beyond what the witness remembers. A stimulus need not itself be admissible merely to revive memory, but this does not authorize evading an exclusion order by reciting excluded contents.

If the witness still cannot remember, a different foundation is needed. For recorded recollection, Fliss, paras. 63–64, requires a reliably made record, a recollection sufficiently fresh when recorded to be probably accurate, present confirmation that the record accurately represented the witness's knowledge then, and use of the original if obtainable. Simply assuming that an earlier entry must have been accurate is insufficient. Another hearsay route may require a different analysis.

A prior inconsistent statement can test the present account. Under Canada Evidence Act s. 10, draw attention to the portions of a recorded statement to be used before introducing contradictory proof. Under s. 11, if the witness does not clearly admit making an inconsistent statement, identify the occasion sufficiently and ask whether it was made before proving it through other evidence. Section 9(2) allows a party to seek leave to cross-examine its own witness about a written or recorded inconsistent statement without first proving adversity. Section 9(1) separately governs an adverse witness. Disappointing testimony alone gives no unrestricted right to attack one's own witness.

Proof that an earlier statement was made does not, without more, establish that its contents were true. The court must identify whether the statement is used for credibility, adopted in testimony, or admitted through another legal route. The hearsay and prior-statements lesson addresses substantive use. Sexual-history and protected-record restrictions also continue to apply during questioning; cross-examination does not bypass those safeguards.

Admit and assess specialized opinion

Qualifications do not complete the admission inquiry

Expert opinion requires a defined subject and a demonstrated need for specialized assistance. Ordinary witnesses generally report what they perceived. Opinion evidence is subject to exclusions and recognized exceptions; specialized knowledge is one such exception. A specialized diagnosis, reconstruction or scientific inference requires the appropriate evidentiary foundation; counsel cannot obtain it simply by asking an ordinary witness for an opinion. White Burgess, paras. 14–15, explains that distinction.

White Burgess Langille Inman v. Abbott and Haliburton Co., 2015 SCC 23, paras. 23–24, describes two stages. The proponent must establish relevance, necessity, the absence of an exclusionary rule and a properly qualified expert. Novel or contested science, or science applied for a novel purpose, also requires the specified reliability assessment. The judge then balances the benefits against risks such as confusion, prejudice and disproportionate time.

The expert must be able and willing to provide impartial, independent and unbiased assistance. White Burgess, paras. 32–34 and 45–54, treats this as an admission issue and an ongoing consideration. An unchallenged acknowledgment of the duty generally suffices initially. The opponent must raise a realistic concern about inability or unwillingness to comply; if it does, the proponent must establish compliance on a balance of probabilities. Clear inability or unwillingness requires exclusion of the affected evidence. Lesser concerns enter the final balancing. Payment or employment by one side does not alone disqualify the witness.

Necessity requires more than usefulness. For unfamiliar science, examine testing, peer review, error rates or standards, and acceptance for the proposed use: R. v. J.-L.J., 2000 SCC 51, paras. 30, 33–35, 56. Acceptance for treatment, for example, does not itself establish reliability for identifying an offender. The scientific label cannot replace proof of the method's suitability.

The permitted field should be stated precisely. Expertise in extracting data from a device does not necessarily qualify the witness to identify the person who typed each message. An admitted opinion remains open to challenges about assumptions, methodology, missing information and its application to the facts. J.-L.J., paras. 56–60, insists on preserving the court's independent assessment: expertise does not authorize merely telling the court that an accused's denial should be believed. The judge or jury remains responsible for deciding the case.

Give the notice required for a fair response

Criminal Code s. 657.3(3) ordinarily requires at least thirty days' notice before trial of the proposed expert's name, area of expertise and qualifications, unless the court fixes another period. The Crown must additionally provide its report or the required opinion summary within a reasonable time before trial. The defence must provide that material no later than the close of the prosecution case.

If an expert is called without compliance, subsection (4) requires, on another party's request, an adjournment for preparation and delivery of the prescribed material. It also requires calling or recalling a witness on related matters unless inappropriate. Even after compliant notice, subsection (5) permits additional preparation measures. Failure to give notice alone does not automatically exclude the opinion.

Section 657.3(1) also permits expert evidence by report with an affidavit or solemn declaration if the court recognizes the expertise and reasonable advance notice and copies are provided. Under subsection (2), the court may still require attendance for questioning. If a proposed defence expert does not testify, subsection (6) prevents the prosecutor from introducing the disclosed material without the accused's consent. Section 7 of the Canada Evidence Act requires leave to call more than five expert witnesses on one side. None of these procedural rules replaces admissibility screening.

Under s. 657.3(7), information disclosed under that section may be used only for the proceeding concerned unless the court orders otherwise.

Practice Checklist

• Identify the witness's personal knowledge and the proposed use of each answer.
• Separate capacity, compulsion, privilege and testimonial accommodations.
• Apply the correct age and disability conditions for each statutory rule.
• Arrange interpretation and authorized aids before testimony where possible.
• Prepare fair questions and a good-faith basis for factual suggestions.
• Distinguish revived memory from reading a prior record.
• State whether an earlier statement is used for credibility or truth.
• Define an expert's field, factual assumptions, duty and notice requirements.