It has been argued that there are issues which simply cannot be decided without expert guidance. Expert opinion evidence is therefore readily received on issues relating to, inter alia, ballistics, engineering, chemistry, medicine, accounting and psychiatry. The question that, however, poses itself is whether expert evidence is in all circumstances necessary.

Phipson (Evidence, 11th edition) and Hoffmann (Evidence, 2nd edition) both point out the dangers inherent in expert testimony. The inability of the court to verify the expert's conclusions and the tendency of experts to be partisan and over-ready to find and multiply confirmation of their theories from harmless facts are problems that can easily occur when accepting expert evidence.

There has been some reluctance to convict an accused solely on the uncorroborated evidence of an expert, but there is no rule that a court cannot make a finding solely on the evidence of an expert. In saying this there are still certain kinds of expert evidence that are treated with more circumspection than others and in the cases of Kunz v Swart 1924 AD 618, Annama v Chetty 1946 AD 142 and recently the case of Levin v Levin 2011 SCA 114 handwriting evidence was treated with caution.

In the case of Levin v Levin (supra) the Supreme Court of Appeal dismissed an appeal against the decision of the South Gauteng High Court which found a will to be valid. Briefly the facts of the case were as follows:

On 3 March 1999 and 8 August 2001 (the 2001 will) respectively, the deceased executed two wills which were in a series of at least nineteen such documents said to have been made by her. The one dated 3 March 1999 dealt with the deceased's assets in Israel which the deceased bequeathed to, the first respondent, being one of her daughters (X) and X's children (the appellants). The 2001 will, related to her assets situated in South Africa and the deceased nominated X as executor (together with her accountant and the Standard Bank of South Africa Ltd) of her estate and granted X and the appellants further, substantial bequests. Under the disputed will, which was dated 4 August 2002, on the other hand, in addition to appointing a new executor, the deceased bequeathed her estate as follows – (a) 25 per cent to each of her children, (b) R50 000 to her doctor and (c) the remainder of her estate to be shared equally among her grandchildren. The purpose of this new will was to restore peace to her family as they would all share equally in the estate upon her death. The appellants brought an action in the court a quo which was then taken on appeal on the basis that the signature on the will was not that of the deceased.

In order to determine the validity of the signature on the will the appellants relied on a reputable hand writing expert to give expert evidence. The expert examined the testatrix's signature on many documents including cheques, letters and the previous wills. In the first of two reports prepared by the expert on the authenticity of the testatrix's signature in the disputed will, he expressed the following view:

"If on 4 August 2002, the deceased's general health had markedly improved – compared with the state of her muscular control and eyesight, demonstrated in the signatures in the will written some twelve months earlier, it is my view, that she was, in all probability, the writer of the disputed signatures. If, however, it can be proved that her eyesight and muscular control had dramatically deteriorated during the intervening period between the penultimate and the questioned will, then there is in my view, a strong possibility that the disputed signatures are very good freehand, simulated forgeries."

What the expert had not been told (after being furnished with further signatures of the deceased), was that the deceased had in fact undergone an eye cataract operation after signing the 2001 will. According to one Dr Deist, corroborated by X, this procedure had significantly improved the deceased's vision and hand-eye coordination. Dr Deist opined that it was reasonable in the light of this improvement to expect the deceased's handwriting to be neater. The expert then conceded that in addition to this operation he was not aware that the deceased was blind in one eye and did not consider the deceased's position when she signed the documents and that all these factors were relevant to his enquiry. While he still nursed some misgivings about the genuineness of the signature in the disputed will, he fairly conceded that he would yield to direct evidence to the effect that the signature was that of the deceased.

The court embarked on one simple enquiry to solve the debate surrounding the signature. Upholding the decisions in Kunz v Swart and Annama v Chetty (supra) the court held that where a judge has arrived at a decision based on the surrounding facts and based on the evidence from direct witnesses, then the evidence from an expert which is in conflict with these two aspects can be disregarded.  

It is safe to say that a judge in a civil or criminal trial cannot play the role of an expert. The parties to an action will call an expert whose function in a trial it is to assist the court to reach a conclusion on matters on which the court itself does not have the necessary knowledge to decide. It is not the mere opinion of the witness which is decisive but his ability to satisfy the court that, because of his special skill, training or experience, the reasons for the opinion which he expresses are acceptable. It is therefore for the court ultimately to decide whether an expert's opinion is to be relied on or not and to determine what weight (if any) has to be given to it.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.