LEGAL PRINCIPLE: EVIDENCE LAW – Expert Evidence – Expert Opinion Is Admissible Though Based on Reports or Information from Others
PRINCIPLE STATEMENT
When an expert expresses opinion about a subject within their expertise, the opinion is admissible even though based on reports made to them or things heard from others, on grounds of relevancy.
RATIO DECIDENDI (SOURCE)
"When Dr. Ogunlesi expressed his opinion about the mental condition of the accused he did so as an expert. The opinion is admissible even though based on report made to him or things heard by others on grounds of relevancy."
EXPLANATION / SCOPE
Expert opinions need not rest solely on the expert’s personal observations. Experts may rely on case histories, reports from others, medical records, and second-hand information—this reflects professional practice where experts regularly rely on such materials. The hearsay rule is relaxed for experts because: (1) such reliance is professionally reasonable; (2) the opinion’s relevance outweighs hearsay concerns; (3) cross-examination can test the expert’s reasoning and reliance basis. However, the underlying reports/information don’t become independently admissible—they remain hearsay but can explain the expert’s opinion basis. Courts assess whether the expert’s reliance was reasonable and conclusions sound. This principle enables realistic expert testimony while maintaining evidentiary standards through cross-examination and weight assessment