Trial Advocacy: Impeachment Of a Witness During Cross-Examination in Nigeria

CONTRIBUTOR: ETIENO UKANGA

Introduction

Trial advocacy encompasses the oral and practical skills a lawyer employs when representing a client before a court, tribunal or other adjudicatory body.^[1] Among the skills that distinguish an accomplished trial lawyer, few are as consequential or difficult to master as cross-examination. Within cross-examination, one of the most effective techniques available to counsel is the impeachment of an opposing witness.

In trial advocacy, impeachment is the process by which counsel uses skilful and legally permissible questioning to challenge the credibility, reliability, consistency or truthfulness of a witness’s testimony. When effectively conducted, impeachment can alter the course of a trial by exposing exaggeration, contradiction, bias or deliberate falsehood, thereby assisting the court in reaching a just determination of the facts in issue.

The Evidence Act, 2011^[2] provides the principal statutory framework governing the impeachment of witnesses in Nigerian courts. The appellate courts have repeatedly emphasised the importance of cross-examination, and by extension impeachment, to the fair and effective administration of civil and criminal justice. In Sanusi v. State,^[3] the Supreme Court held that where a party fails to challenge a witness’s evidence under cross-examination, the evidence remains uncontroverted. Accordingly, where a witness makes a statement that materially conflicts with their testimony in court and fails to provide a satisfactory explanation for the inconsistency, the court may regard the witness as unreliable and reject the affected evidence.

Similarly, in Akanbi v. Alatede (Nig.) Ltd,^[4] the Court of Appeal held that a document intended to impeach the credibility of a witness becomes admissible once the party seeking to rely on it satisfies the relevant conditions precedent. The document need not necessarily have been tendered during the witness’s cross-examination.^[5]

This article examines the principles, techniques and legal framework governing the impeachment of witnesses during cross-examination in Nigeria. It analyses witness impeachment as an essential trial advocacy tool and considers the relevant provisions of the Evidence Act 2011 relating to prior inconsistent statements, contradictory testimony, bias and previous convictions. It also examines the procedural requirements that counsel must satisfy before impeaching a witness. Particular attention is given to the strategic use of cross-examination to expose inaccuracies, exaggerations and falsehoods in witness testimony while preserving fairness, professional ethics and the integrity of judicial proceedings.

The Concept of Witness Impeachment in Trial Advocacy

Witness impeachment is the process of challenging or undermining a witness’s credibility during trial by presenting evidence or asking questions that expose contradictions, bias, inconsistency or falsehood in the witness’s testimony.^[6] Section 233 of the Evidence Act 2011 provides that any party other than the party who called the witness may impeach the witness’s credibility. The party who called the witness may also do so with the court’s consent. Under the section, a witness’s credibility may be impeached by evidence from persons who, based on their knowledge of the witness, consider the witness unworthy of credit; proof that the witness has been bribed, accepted an offer of a bribe or received another corrupt inducement to testify; or proof of previous statements inconsistent with any part of the witness’s testimony that may lawfully be contradicted.^[7]

Properly understood, witness impeachment is not a single technique but a range of related techniques directed towards a common objective: discrediting all or part of a witness’s testimony in the estimation of the court. Counsel may challenge a witness’s credibility by exposing inconsistencies in the witness’s account, demonstrating bias or interest, establishing prior conduct relevant to truthfulness or otherwise questioning the reliability of the witness as a source of accurate and truthful evidence.^[8]

During cross-examination, counsel may question a witness about specific conduct that bears directly on the witness’s credibility, subject to the applicable rules of evidence and the court’s control over improper or irrelevant questioning. The purpose is not merely to attack the witness personally but to provide the court with a legitimate basis for assessing the weight and reliability of the testimony.

In Mustapha v. Bulkachuwa,^[9] the Court of Appeal held that evidence thoroughly discredited under cross-examination requires no further rebuttal. Conversely, where material evidence remains unchallenged under cross-examination, the court may treat it as uncontroverted and act upon it, provided that the evidence is credible and capable of supporting the relevant finding.^[10]

Impeachment of a Witness During Cross-Examination in Nigeria

Cross-examination is a powerful forensic tool through which counsel tests the accuracy, credibility and reliability of an opposing witness’s testimony. When skilfully conducted, it may expose inconsistencies, exaggerations and falsehoods capable of weakening or even undermining the opposing party’s case. Evidence elicited during cross-examination forms part of the evidence before the court and carries the same evidential value as testimony given during examination-in-chief. In appropriate circumstances, answers obtained under cross-examination may prove particularly persuasive because they emerge from a direct and searching examination of the witness’s account.^[11]

A witness may be cross-examined about a previous written statement, or a statement reduced into writing, that relates to a matter in issue in the suit or proceeding. Counsel may question the witness about the statement without first showing or proving the document. However, where counsel intends to contradict the witness with the written statement, counsel must first draw the witness’s attention to the specific portions intended to be used for that purpose before tendering the statement in evidence.

The previous statement becomes admissible for impeachment only where the witness denies making it or disputes its relevant contents. Where the witness admits making the statement and acknowledges the material contents relied upon, there is ordinarily no contradiction requiring the statement to be tendered solely for impeachment.^[12]

The object of cross-examination is to test the truth of a witness’s testimony and weaken the opposing party’s case where the evidence proves unreliable.^[13] Counsel may impeach a witness during cross-examination by confronting the witness with contradictory evidence or a previous inconsistent statement. In AKPUTA v. STATE,^[14] the Supreme Court held that where a prosecution witness gives evidence on a material point that the opposing party intends to challenge, counsel must put the substance of the contradictory evidence to the witness during cross-examination or, at the very least, indicate that the evidence is not accepted as true.^[15] This principle promotes fairness, prevents surprise and assists the court in its search for the truth. Accordingly, where a party fails to cross-examine a witness on a material point, the court may infer that the party accepts the evidence.^[16]

A witness may also be impeached by reference to a previous written statement that is inconsistent with their testimony in court. The statement must have been made in writing by the witness or reduced into writing. The purpose of confronting the witness with the inconsistency is to challenge the witness’s credibility and the reliability of the testimony.^[17]

Section 232 of the Evidence Act 2011 provides:

A witness may be cross-examined as to previous statements made by him in writing or reduced into writing, and relevant to matters in question in the suit or proceeding in which he is cross-examined, without such writing being shown to him or being proved; but, if it is intended to contradict him by the writing, his attention must, before the writing can be proved, be called to those parts of it which are to be used for the purpose of contradicting him.^[18]

Where the previous statement forms part of the witness’s testimony in the same proceedings and the witness denies making it, counsel may request the court to have the relevant portion read to the witness. Where the witness denies making a previous written statement, counsel must confront the witness with the specific portion that is inconsistent with the testimony given in court. In practical terms, counsel should read the relevant passage to the witness and allow the witness to admit, deny or explain the inconsistency before seeking to tender the statement in evidence.^[19]

The court may, at any stage of the trial, direct that the previous inconsistent statement be produced for its inspection. It may also use the statement in any manner permitted by law in determining the credibility of the witness and the weight to attach to the testimony.^[20]

Procedural Requirements for Impeaching a Witness

Nigerian law prescribes specific procedural requirements that counsel must satisfy when impeaching a witness, particularly through a previous inconsistent statement. As earlier noted, the Evidence Act 2011 requires counsel to draw the witness’s attention specifically to the relevant portions of the previous statement before proving the statement against the witness. This requirement, commonly described as the duty to “put” the contradiction to the witness, promotes fairness by allowing the witness to admit, deny or explain the apparent inconsistency. It also enables the trial court to assess both the contradiction and any explanation offered by the witness.

In Otti v. State,^[21] while considering the procedure for impeaching the credibility of a witness, the Court of Appeal held:

“Under section 209(c) of the Evidence Act, the credit of a witness may be impeached by proof of former statements inconsistent with any part of his evidence which is liable to be contradicted.^[22]

Similarly, in Olali v. Nigerian Army,^[23] the Court of Appeal held:

Where a party intends to impeach the credibility of a witness, counsel must confront the witness with the relevant evidence while the witness is still in the witness box. It is improper for defence counsel to refrain from cross-examining a witness on a material point and later seek to challenge that evidence by calling oral or documentary evidence after the prosecution has closed its case. In a criminal trial, the defence must challenge, through cross-examination, every aspect of the evidence it intends to dispute. Where evidence has been lawfully admitted, and the accused person seeks to contest it, the proper opportunity to do so arises while the witness is testifying. Counsel must cross-examine the witness on the disputed facts, as it is too late at the close of the case to attempt to contradict evidence that was left unchallenged.

The Strategic Role of Cross-Examination and Professional Ethics

The strategic use of impeachment techniques is one of the most demanding aspects of trial advocacy. It requires meticulous preparation, a sound knowledge of the rules of evidence, insight into witness behaviour and the discipline to keep questioning within a legitimate forensic purpose. Effective impeachment rarely results from a single dramatic confrontation. More often, it develops through careful and progressive questioning that narrows the witness’s scope for evasion before counsel exposes the decisive contradiction or secures the relevant admission.

Nigerian legal practitioners must also observe the professional and ethical rules governing cross-examination and the impeachment of witnesses. The Rules of Professional Conduct for Legal Practitioners 2023 require legal practitioners to conduct litigation fairly, candidly and with due regard for the administration of justice. Counsel must not use cross-examination to harass or intimidate a witness or to pursue objectives unrelated to the fair determination of the issues before the court.^[24]

Conclusion

The impeachment of a witness during cross-examination occupies a central place in Nigerian trial advocacy. It provides an important means by which the adversarial process tests the credibility, reliability and truthfulness of testimony. Through impeachment, counsel may expose inconsistency, bias, interest or falsehood and thereby assist the court in determining the facts and administering justice between the parties.

The Evidence Act 2011 provides the statutory framework for impeaching witnesses through previous inconsistent statements, cross-examination on written statements, proof of bias or interest and other recognised methods of challenging credibility. These methods remain subject to procedural safeguards intended to ensure fairness to the witness while protecting the legitimate interests of the cross-examining party. Counsel must therefore combine strategic skill with strict compliance with evidential rules and professional ethics. When properly conducted, impeachment strengthens the fact-finding process; when improperly used, it may undermine the fairness and integrity of the proceedings.

Reference:

1. A. Obi Okoye, Law in Practice in Nigeria (3^rd Edition; Memoiyke Publishing Nig. Ltd, Enugu, 2021) P. 291 ↑
2. Evidence Act, 2011, Cap E14, Laws of the Federation of Nigeria, 2011 (hereinafter “Evidence Act” or “the Act”). ↑
3. (2023) 10 NWLR (Pt. 1892) 253 ↑
4. (2000) 1 NWLR (Pt. 639) 125 ↑
5. Madumere v. Okafor (1996) 4 NWLR (Pt.445) 637, (P. 142, paras. (2-D) ↑
6. LII, ‘Impeachment of Witness’ (2026) https://www.law.cornell.edu/wex/impeachment_of_a_witness accessed 21 June, 2026. ↑
7. Evidence Act 2011, section 233 ↑
8. Ibid. ↑
9. (2020) 12 NWLR (Pt. 1739) 391 ↑
10. MAUTECH v. Yarai (2020) 15 NWLR (Pt. 1748) 395 ↑
11. Oforlete v. State (2000) 12 NWLR (Pt. 681) 415; Ayan v. State (2013) 15 NWLR (Pt. 1376) 34; Gaji v. Paye (2003) 8 NWLR (Pt. 823) 583; Akomolafe v. Guardian Press Ltd. (2010) 3 NWLR (Pt. 1181) 338; Omisore v. Aregbesola (2015) 15 NWLR (Pt. 1482) 205; Adeosun v. Gov., Ekiti State (2012) 9 NWLR (Pt. 1291) 581; Okuleye v. Adesanya (2014) 12 NWLR (Pt. 1422) 321 referred to.] (P. 402, paras. A-C) ↑
12. Ekang v. State (2001) 11 NWLR (Pt. 723) 1 ↑
13. Opeke v. State (2021) 1 NWLR (Pt. 1758) 570 ↑
14. (2024) LPELR-62193(SC) ↑
15. See Babalola v. State [1989] 4 NWLR (Pt 115) 264; Nwobodo v. Onoh (1984) 1 SCNLR 1 at 88, ↑
16. Oforlete v. State (2000) LPELR-2270 (SC); Esene v. The State (2017) LPELR-41912 (SC); (1989) LPELR-695 (SC); Aliyu v. State (2013) LPELR-20748 (SC); Suleiman v. State (2022) LPELR-57577 (SC).” Per JOHN INYANG OKORO, JSC (Pp 25 – 25 Paras A – E) ↑
17. Ibid, A. Obi Okoye, Law in Practice in Nigeria, pp.303-304 ↑
18. Evidence Act 2011, section 232 ↑
19. Ibid, A. Obi Okoye, Law in Practice in Nigeria, pp.303-304 ↑
20. Ibid, Proviso, s. 232 ↑
21. (1991) 8 NWLR (Pt. 207) 103 ↑
22. Adisa v. State (1964) 1 All NLR 200; Joshua v. Queen (1964) 1 All NLR 1; Arehia v. State (1982) 4 S.C. 78 referred to]. (Pp.120-121, paras. H-A). ↑
23. (2016) 4 NWLR (Pt. 1502) 358 ↑
24. Rules of Professional Conduct for Legal Practitioners, 2023. ↑