Ordinarily the opinion of a witness is irrelevant and inadmissible in evidence. Opinion refers to ideas, a belief or judgment based mainly on feelings. A witness called to testify in any judicial proceedings cannot give his opinion as to the existence or non-existence of a fact in issue or relevant fact.
A witness can only testify to facts known to him not to his opinion as a court of law deals only with fact and not opinions, speculations, gossips, suggestions or pieces of advice; See Section 67 of the Evidence Act and the case of R. V. Loake (1911)7 Cr. APP Rep. 71.
See also:- Estoppel; Private Privilege; States Privilege; Presumption and Rebuttable Presumption of law; Facts Judicially Noticed; Matters that need not be Proved by Evidence and Sources of Nigeria Law of Evidence
Exceptions to Opinion evidence
- Opinions of experts
- Opinions of non-experts
- Opinion of Experts: The Act permits the reception of opinion of experts when the court has to form an opinion upon a point of foreign law, customary law or custom, or of science or art, or as to identify a handwriting or finger impressions. These are matters calling for special knowledge.
Thus, whenever the has to determine any issue falling within the fields covered by the provision of Section 68, evidence of an expert is relevant and ipso facto, admissible.
Section 68(2) says “To qualify as an expert a witness must be specially skilled in the field in which he is given evidence and the test must always be the knowledge and experience of the particular witness and whether the evidence justifies the conclusion that he is specially skilled, which means no more than that, he has special knowledge, training or experience in the matter or question” See the case of Azu V. State (1993)7 SCNJ (pt 1)151 thus for a person to be regarded as an expert, he must have made a special study of the subject or acquired a special experience therein. See the case of Seismograph Service Ltd V. Onolepata.
It is the duty of the court to determine who is an expert
- Opinion as to foreign law: Section 69 of the Evidence Act, 2011 “Where there is a question as to foreign law, the opinions of experts who in their profession are acquainted with such law are admissible evidence of it, though such experts may produce to the court books which they declare to be works of authority upon the foreign law in question, which books the court, having received all necessary explanations from the experts, may construe for itself.
- Opinion on customary law and custom: Section 70 “in deciding questions of customary law and custom, the opinions of traditional rulers, chiefs or other persons having special knowledge of the customary law and custom and any book or manuscript recognized as legal authority by people indigenous to the locality in which such law or custom applies, are admissible.
- Opinion on point of science or Arts: Section 68 (1) when the court has to form an opinion upon a point of foreign law, customary law or custom, or of science or art, or as to identity of handwriting or finger impressions, the opinions upon that point of persons specially skilled in such foreign law, customary law or custom, or finger impressions, are admissible. (2) Persons so specially skilled as mentioned in subsection (1) of this section are called experts.
Opinion as to handwriting and finger impression: Section 72
(1) when the court has to form an opinion as to the person by whom any document was written or signed; the opinion of any person acquainted with the handwriting of the person by whom it is supposed to be written or signed that it was or was not written or signed by that person, is admissible.
(2) A person is said to be acquainted with the handwriting of another person when he had seen that person write, or when he has received documents purporting to be written by that person in answer to documents written by himself or under his authority and addressed to that person, or when in the ordinary course of business, documents purporting to be written by that person have been habitually submitted to him.
2. Opinion of non-experts: Are admissible in the following instances:-
a. Opinion as to handwriting
b. Opinion as to existence of general custom or write Section 73(1)
c. Opinion as to usage and tenets
d. Opinion as to relationships
Under opinions not provided in the Act
- Opinion as to age: the evidence of a mother or father or of a person present at a birth is admissible as long as it is unchallenged.
- Opinion as to speed: see the case of Akinrinmade V. Lawal (1996)2 NWLR (pt 429)218 (VIO)
- Opinion as to the value: The opinion of a lay man as to the value of a property is admissible.
- Opinion as to Identity: Identification of a person or object may become relevant in any judicial proceedings. When this arises witness are permitted to identify the person or thing.
- Opinion as to intoxication: When it is relevant to determine whether or not a person was intoxicated a non-expert witness especially police officer are permitted to testify that the relevant person was intoxicated at the relevant time.
- Opinion as to mental and Physical health: A lay witness may be permitted to testify as to his own condition of health mental and physical. When a witness testifies as to his health he is offering opinion evidence but he will not be permitted to testify as to the conditions of health of other persons. See the case of Adekunle V. State and State V. Alexander.