In both criminal and civil cases, the general rule is that a witness may only testify as to matters of fact of which they have personal knowledge. Thus, a witness may not draw inferences from the facts, speculate about the causes of the facts or make value judgments about those facts. The case of Kahale is unusual in that the expert who was required to give evidence, i.e., the ballistics expert, did not do so whilst PW7, a non-expert, was permitted to give evidence that required an expert in the relevant field. There was therefore a complete absence of expert opinion evidence and yet this was of critical importance to the case. In cases, especially those which rest entirely on circumstantial evidence as was the case here, expert opinion evidence is often crucial.
"Enock Kahale & 3 Others v The People  ZMCA 26,"
SAIPAR Case Review: Vol. 4
, Article 4.
Available at: https://scholarship.law.cornell.edu/scr/vol4/iss1/4