Opinion evidence

Opinion evidence refers to evidence of what the witness thinks, believes, or infers in regard to facts, as distinguished from personal knowledge of the facts themselves. In common law jurisdictions the general rule is that a witness is supposed to testify as to what was observed and not to give an opinion on what was observed. However, there are two exceptions to this rule: expert evidence and non-expert opinion given by laymen which people in their daily lives reach without conscious ratiocination.