As a general rule under Nigerian law of Evidence, the opinion evidence is irrelevant in court trials. Thus section 66 of the Evidence Act CAP E14, Laws of the. Federation of Nigeria (LFN), 2004 provides that the fact that any person is of the opinion that a fact in issue, or relevant to the issue, does or does not exist, is irrelevant to the existence of such fact except as provided in sections 57 to 65 of the Evidence Act.
Exceptions to this general rule are contained in sections 57 to 65 of the Evidence Act, which make opinion of experts and non-experts relevant with regard to foreign law, native law and custom, points of science or art, identity of hand-writing or finger impressions, native law and custom, certain usages and tenets, existence of the relationship of one person to another, etc. Section 57 subsections (1) and (2) specifically provides:
“(1) When the court has to form an opinion upon a point of foreign law, native 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, native law or custom, or science or art, or in questions as to identity of handwriting or finger impressions, are relevant facts. (2) Such persons are called experts”
The need for experts or persons specifically trained or qualified in particular discipline to assist the court by testifying on causation arising from certain phenomenon studied by them is acknowledged by this section (section 57 (1)) --- i.e., expert opinion (in oral or written form) is admissible under section 57 of the Evidence Act. Expert opinion is particularly very necessary where the phenomenon being inquired into by the court is beyond the knowledge of a mind (e.g., judges, magistrates and judicial officers) untrained in the discipline or art concerned.
As an example, in the Nigerian case of Seismograph Service v. Ogbeni (1976)1 NMLR 290, the court held that evidence of an expert was absolutely necessary to prove damage alleged to be caused by vibrations from seismic operations taking place within a reasonable distance from the property damaged, these being phenomena beyond the knowledge of the unscientific and the untrained in seismology and civil engineering.
See also the United States case of Lorraine v Markel Am. Insurance Co, 241 FRD 534 (D. Md. 2007), where the court admitted the opinion of experts in order to ascertain if the damage to Lorraine’s yacht was caused by lightning. Thus section 60 of the Evidence Act provides that where the opinions of experts are relevant, facts, not otherwise relevant, become relevant and admissible if they support or are inconsistent with such expert opinions.
HOW TO TENDER EXPERT EVIDENCE To be admissible, expert opinion must be -a) given or tendered directly by the expert himself; or b) where the opinion is already expressed in a treatises or book commonly offered for sale, the opinion may be proved by production of such treatise or book if (i) the author is dead or (ii) cannot be found or (iii) is incapable of giving evidence or (iv) cannot be called as a witness without an amount of delay or expense which the court regards as unreasonable. (see section 77 (d) (i) of the Evidence Act) Section 77 (d) (i) of the Evidence Act provides: “Oral evidence must, in all cases whatever, be direct – (d) if it refers to an opinion or to the grounds on which that opinion is held, it must be the evidence of the person who holds that opinion on those grounds:
Provided that – (i) the opinions of experts expressed in any treatise commonly offered for sale, and the grounds on which such opinions are held, may be proved by the production of such treatise if the author is dead or cannot be found, or has become incapable of giving evidence, or cannot be called as a witness without an amount of delay or expense which the court regards as unreasonable, WHO IS AN EXPERT WITNESS?
An expert is a person specially skilled in any of the fields/areas mentioned in section 57 (1) above or the area on which he (the expert) gives evidence. It is important to note that it is principally the duty of the court to determine who is an expert, ie, whether a person is sufficiently skilled to give expert evidence. (see the case of R v. Onitiri (1946) 12 WACA 58 at 59); see also section 186 of the Evidence Act).
The court is assisted in discharging this duty by the expert witness stating his qualification and experience before leading evidence. See the case of Azu v. The State (1993) 6 NWLR (Pt. 299) page 303. It should also be noted that the skill required for this purpose is not necessarily acquired by academic qualification or training; it may also be by experience (Shell Petroleum Development Co. (Nig) Ltd. V. Tiebo (1996), 4 NWLR (pt. 445) P. 657). Although the court will normally accept an un-contradicted expert evidence
( Siesmograph Service (Nig) Ltd V. Apkororo (1974) 6 SC 119), it will not be bound to do so where such opinion conflicts with common sense (Okoh v. The State. (1971) NMLR 140) or where the expert fails to state the basis of his opinion (Idudhe v. Eseh (1996) 5 NWLR (Pt. 451) P. 750). The correct test of the relevance of the witness`s opinion as that of an expert is whether he is specially skilled on the particular field in question (Siesmograph Service (Nig) Ltd. V. Onakpasa (1972) 1 ANLR (part 1) 343.
Where evidence of an expert on a particular field is relevant, whether a person who claims to be an expert in that field would be allowed to testify would depend on the following: a) He must first of all state his qualification and satisfy the court that he is an expert on the subject in which he is to give his opinion; b) He must state clearly the reasons for his opinion. There must be enough materials before the court to warrant treating a witness as an expert and the reception of his evidence as relevant evidence; the requisite materials the court may need for this purpose may include such facts as --a) The witness`s credentials;
b) His experiences c) Training; d) The nature of the duty of his office in relation to the subject in which he is to offer his opinion. Consequently, a witness, in order to be competent as an expert, need not be a specialist or an expert in the professional sense; it is sufficient if he has made a special study of the subject or acquired a special experience in it. OPINION OF AN EXPERT ON POINT OF SCIENCE OR ART (such as DNA, medicine, digital forensic examination, engineering, computer, electronic or digital technology, etc)
Opinion of experts specially skilled in the area of science or arts is relevant where the court is to form an opinion on a point of science or art (see S. 57 (1) of the Evidence Act). The term science or art includes not only the well established discipline and branches of knowledge under these two headings but also almost any matter which is the subject of special knowledge (Folkes v. Chadd (1782) 3 Dough 157. The terms science and art are used broadly and include determination of cause of death or the distance from which the fatal missile was launched, both of which have been held to be within the competence of a medical doctor ( Oguonzee v.
The State (1998) 5 NWLR (Pt. 551) P. 521). Note however that the subject must be one upon which competency to form an opinion can only be acquired by a course of special study or experience (R v. Coleman, 6 Cox 163). SCOPE AND EFFECT OF EXPERT EVIDENCE The function of the expert is to assist the court in reaching a correct decision. He gives his opinion upon facts which are either admitted or proved by himself or other witness in his hearing at the trial of a case. The opinion may also be on hypothesis based on the evidence.
B ut where the opinion is based on report of fact, these facts must be proved independently, that is, by calling witnesses who are personally concerned in the transaction (see Uwa Printers Ltd v. Investment Trust Ltd (1988) 5 NWLR 110; Ramsdale v. Ramsdale (1945) 173 LT 393; R v. Somers (1963) WLR 1306). Thus section 65 of the Evidence Act provides that whenever the opinion of any living person is relevant, the grounds on which such opinion is based are also relevant. So the expert witness must base his evidence on such facts, which themselves must necessarily be in evidence before the court (see Onuorah v. State (1988) 3 NWLR 486).
As it is the function of the court to make findings on the facts in issue in the case before the court, the opinion of expert witnesses should be restricted to technical or scientific matters relevant to the determination of this finding. Thus, as the issue of whether an accused person is sane or insane in a legal sense at the time when the act was committed is a question of fact to be determined by the judge, a psychiatrist called as a witness for the defence should not be directly asked to give his opinion as to the state of the accused person`s mind at the time of the offence, but he (the expert psychiatrist) may give evidence from which such state of mind at the material time may be inferred.
Where the issue is whether a treatment by a medical doctor was negligent, the expert witness may give evidence of his opinion that the treatment was unorthodox, but not that it was negligent, which is the very issue the court has to determine. Where however the issue to be determined by the court is essentially a scientific or technical one or calls for a particular skill, the expert may give an opinion on that very issue if he has himself observed the facts (Martin v. Johnson (1858) 1 F & F 122).
The opinion of an expert should be restricted to matters particularly within his knowledge as such expert. Any opinion outside his limit is inadmissible (see Wallace-Johnson v. R (1936) 3 WACA 104). Again, a court is not bound to accept the evidence of opinion by an expert (see R v. Jennion (1962) 1 WLR 317). But if it is uncontradicted and there is no other evidence on the issue, the court may not likely reject it; the court should admit such evidence if it is not shaken under cross-examination and is uncontradicted (Elf Nig Ltd v. Sillo (1994) 7-8 SCNJ 119 at 133). Note however that expert evidence does not automatically become accepted because it is unchallenged. Such may be rejected if there exist good reasons to do so (AG, Oyo State v. Fairlakes Hotels (No 2) (1989) 5 NLR 255 at 291—292).
Where there is a conflict of expert opinions, the court is bound to resolve the conflict by accepting one shade of expert opinion and rejecting the other (Oyakhue v. Obaseki (1986) 1 NWLR 735 at 742. Again, in criminal cases, a conviction could be based solely on the evidence of one expert opinion without more (R v.
Atkinson (1936) 13 NLR 71. In summary, a certified or experienced computer forensics examiner could qualify as an expert witness under section 57 subsections (1) and (2) of the Nigerian Evidence Act and be so admitted by Nigerian courts. It is advisable that computer forensics examiners familiarize themselves with the rules of evidence and civil/criminal procedure rules as applied by Nigerian courts or be guided by their lawyer in order to creditably practice their profession.
Philip O Nwachukwu is a digital forensics examiner and CEO of SystemTrust. He is a member, NOUN Law Society and also a member of Computer Forensics Institute, Nigeria.
E‐mail: [email protected]‐ng.com
Evidence Act, Cap E14, Laws of the. Federation of Nigeria (LFN), 2004 Aguda, Akinola, The law of Evidence, Ibadan, Spectrum Books Limited, 1966 Udemezue S, Expert Witness in Law of Evidence, Nigerian Law School (unpub) 2009 PAUL W. GRIMM, CHIEF UNITED STATES MAGISTRATE JUDGE: Ratio Decidendi in Lorraine v Markel Am Ins Co 241 FRD 534 (D.Md. 2007)