Wis. Stat. § 906.01 General rule of competency
Every person is competent to be a witness except as otherwise provided in these rules.
Evidence — witnesses
Wis. Stat. ch. 906
in effectWis. Stat. § 906.02 Lack of personal knowledge
A witness may not testify to a matter unless evidence is introduced sufficient to support a finding that the witness has personal knowledge of the matter. Evidence to prove personal knowledge may, but need not, consist of the testimony of the witness. This rule is subject to the provisions of s. 907.03 relating to opinion testimony by expert witnesses.
Wis. Stat. § 906.03 Oath or affirmation
(1) Before testifying, every witness shall be required to declare that the witness will testify truthfully, by oath or affirmation administered in a form calculated to awaken the witness’s conscience and impress the witness’s mind with the witness’s duty to do so.
(2) The oath may be administered substantially in the following form: Do you solemnly swear that the testimony you shall give in this matter shall be the truth, the whole truth and nothing but the truth, so help you God.
(3) Every person who shall declare that the person has conscientious scruples against taking the oath, or swearing in the usual form, shall make a solemn declaration or affirmation, which may be in the following form: Do you solemnly, sincerely and truly declare and affirm that the testimony you shall give in this matter shall be the truth, the whole truth and nothing but the truth; and this you do under the pains and penalties of perjury.
(4) The assent to the oath or affirmation by the person making it may be manifested by the uplifted hand.
Wis. Stat. § 906.04 Interpreters
An interpreter is subject to the provisions of chs. 901 to 911 relating to qualification as an expert and the administration of an oath or affirmation that the interpreter will make a true translation.
Wis. Stat. § 906.05 Competency of judge as witness
The judge presiding at the trial may not testify in that trial as a witness. No objection need be made in order to preserve the point.
Wis. Stat. § 906.06 Competency of juror as witness
(1) At the trial. A member of the jury may not testify as a witness before that jury in the trial of the case in which the member is sitting as a juror. If the juror is called so to testify, the opposing party shall be afforded an opportunity to object out of the presence of the jury.
(2) Inquiry into validity of verdict or indictment. Upon an inquiry into the validity of a verdict or indictment, a juror may not testify as to any matter or statement occurring during the course of the jury’s deliberations or to the effect of anything upon the juror’s or any other juror’s mind or emotions as influencing the juror to assent to or dissent from the verdict or indictment or concerning the juror’s mental processes in connection therewith, except that a juror may testify on the question whether extraneous prejudicial information was improperly brought to the jury’s attention or whether any outside influence was improperly brought to bear upon any juror. Nor may the juror’s affidavit or evidence of any statement by the juror concerning a matter about which the juror would be precluded from testifying be received.
Wis. Stat. § 906.07 Who may impeach
The credibility of a witness may be attacked by any party, including the party calling the witness.
Wis. Stat. § 906.08 Evidence of character and conduct of witness
(1) Opinion and reputation evidence of character. Except as provided in s. 972.11 (2), the credibility of a witness may be attacked or supported by evidence in the form of reputation or opinion, but subject to the following limitations:
(a) The evidence may refer only to character for truthfulness or untruthfulness.
(b) Except with respect to an accused who testifies in his or her own behalf, evidence of truthful character is admissible only after the character of the witness for truthfulness has been attacked by opinion or reputation evidence or otherwise.
(2) Specific instances of conduct. Specific instances of the conduct of a witness, for the purpose of attacking or supporting the witness’s character for truthfulness, other than a conviction of a crime or an adjudication of delinquency as provided in s. 906.09, may not be proved by extrinsic evidence. They may, however, subject to s. 972.11 (2), if probative of truthfulness or untruthfulness and not remote in time, be inquired into on cross-examination of the witness or on cross-examination of a witness who testifies to his or her character for truthfulness or untruthfulness.
(3) Testimony by accused or other witnesses. The giving of testimony, whether by an accused or by any other witness, does not operate as a waiver of the privilege against self-incrimination when examined with respect to matters which relate only to character for truthfulness.
Wis. Stat. § 906.09 Impeachment by evidence of conviction of crime or adjudication of delinquency
(1) General rule. For the purpose of attacking character for truthfulness, a witness may be asked whether the witness has ever been convicted of a crime or adjudicated delinquent and the number of such convictions or adjudications. If the witness’s answers are consistent with the previous determination of the court under sub. (3), then no further inquiry may be made unless it is for the purpose of rehabilitating the witness’s character for truthfulness.
(2) Exclusion. Evidence of a conviction of a crime or an adjudication of delinquency may be excluded if its probative value is substantially outweighed by the danger of unfair prejudice. Factors for a court to consider in evaluating whether to admit evidence of prior convictions for the purpose of attacking a witness’s truthful character include:
(a) The lapse of time since the conviction.
(b) The rehabilitation or pardon of the person convicted.
(c) The gravity of the crime.
(d) The involvement of dishonesty or false statement in the crime.
(e) The frequency of the convictions.
(f) Any other relevant factors.
(3) Admissibility of conviction or adjudication. No question inquiring with respect to a conviction of a crime or an adjudication of delinquency, nor introduction of evidence with respect thereto, shall be permitted until the court determines pursuant to s. 901.04 whether the evidence should be excluded.
(5) Pendency of appeal. The pendency of an appeal therefrom does not render evidence of a conviction or a delinquency adjudication inadmissible. Evidence of the pendency of an appeal is admissible.
Wis. Stat. § 906.10 Religious beliefs or opinions
Evidence of the beliefs or opinions of a witness on matters of religion is not admissible for the purpose of showing that by reason of their nature the witness’s credibility is impaired or enhanced.
Wis. Stat. § 906.11 Mode and order of interrogation and presentation
(1) Control by judge. The judge shall exercise reasonable control over the mode and order of interrogating witnesses and presenting evidence so as to do all of the following:
(a) Make the interrogation and presentation effective for the ascertainment of the truth.
(b) Avoid needless consumption of time.
(c) Protect witnesses from harassment or undue embarrassment.
(2) Scope of cross-examination. A witness may be cross-examined on any matter relevant to any issue in the case, including credibility. In the interests of justice, the judge may limit cross-examination with respect to matters not testified to on direct examination.
(3) Leading questions. Leading questions should not be used on the direct examination of a witness except as may be necessary to develop the witness’s testimony. Ordinarily leading questions should be permitted on cross-examination. In civil cases, a party is entitled to call an adverse party or witness identified with the adverse party and interrogate by leading questions.
Wis. Stat. § 906.12 Writing used to refresh memory
If a witness uses a writing to refresh the witness’s memory for the purpose of testifying, either before or while testifying, an adverse party is entitled to have it produced at the hearing, to inspect it, to cross-examine the witness thereon, and to introduce in evidence those portions which relate to the testimony of the witness. If it is claimed that the writing contains matters not related to the subject matter of the testimony, the judge shall examine the writing in camera, excise any portions not so related, and order delivery of the remainder to the party entitled thereto. Any portion withheld over objections shall be preserved and made available to the appellate court in the event of an appeal. If a writing is not produced or delivered pursuant to order under this rule, the judge shall make any order justice requires, except that in criminal cases when the prosecution elects not to comply, the order shall be one striking the testimony or, if the judge in the judge’s discretion determines that the interests of justice so require, declaring a mistrial.
Wis. Stat. § 906.13 Prior statements of witnesses
(1) Examining witness concerning prior statement. In examining a witness concerning a prior statement made by the witness, whether written or not, the statement need not be shown or its contents disclosed to the witness at that time, but on request the same shall be shown or disclosed to opposing counsel upon the completion of that part of the examination.
(2) Extrinsic evidence of prior inconsistent statement of a witness.
(a) Extrinsic evidence of a prior inconsistent statement by a witness is not admissible unless any of the following is applicable:
1. The witness was so examined while testifying as to give the witness an opportunity to explain or to deny the statement.
2. The witness has not been excused from giving further testimony in the action.
3. The interests of justice otherwise require.
(b) Paragraph (a) does not apply to admissions of a party-opponent as defined in s. 908.01 (4) (b).
Wis. Stat. § 906.14 Calling and interrogation of witnesses by judge
(1) Calling by judge. The judge may, on the judge’s own motion or at the suggestion of a party, call witnesses, and all parties are entitled to cross-examine witnesses thus called.
(2) Interrogation by judge. The judge may interrogate witnesses, whether called by the judge or by a party.
(3) Objections. Objections to the calling of witnesses by the judge or to interrogation by the judge may be made at the time or at the next available opportunity when the jury is not present.
Wis. Stat. § 906.15 Exclusion of witnesses
(1) At the request of a party, the judge or a circuit court commissioner shall order witnesses excluded so that they cannot hear the testimony of other witnesses. The judge or circuit court commissioner may also make the order of his or her own motion.
(2) Subsection (1) does not authorize exclusion of any of the following:
(a) A party who is a natural person.
(b) An officer or employee of a party which is not a natural person designated as its representative by its attorney.
(c) A person whose presence is shown by a party to be essential to the presentation of the party’s cause.
(d) A victim, as defined in s. 950.02 (4), in a criminal case or a victim, as defined in s. 938.02 (20m), in a delinquency proceeding under ch. 938, unless the judge or circuit court commissioner finds that exclusion of the victim is necessary to provide a fair trial for the defendant or a fair fact-finding hearing for the juvenile. The presence of a victim during the testimony of other witnesses may not by itself be a basis for a finding that exclusion of the victim is necessary to provide a fair trial for the defendant or a fair fact-finding hearing for the juvenile.
(3) The judge or circuit court commissioner may direct that all excluded and non-excluded witnesses be kept separate until called and may prevent them from communicating with one another until they have been examined or the hearing is ended.
Wis. Stat. § 906.16 Bias of witness
For the purpose of attacking the credibility of a witness, evidence of bias, prejudice, or interest of the witness for or against any party to the case is admissible.
Source: WI Statutes (Official Site)URL: https://docs.legis.wisconsin.gov/statutes/statutes/906Fetched: 10/7/2026