Can lay people give more weight than experts in their opinion of a testator's mental capacity?

A strong statement supporting the proposition that, in some cases, the opinion of lay people concerning a testator's mental capacity may be given more weight than the opinion of experts is found in the concurring reasons of Mr. Justice Laidlaw in Spence v. Price, supra, at 595-596: Because of the emphasis put in argument by counsel for the appellant on the evidence given by doctors in this case, I desire to express my views in respect of that matter. The quality of a person's mind manifests itself by conduct and expressions of thought. The conclusions to be reached from such evidence do not depend for their correctness upon the possession or exercise of special skill or knowledge. A judgment may be formed by a person of sound mind and reason exercising powers of observation and deduction without the use of any scientific learning whatever. It is a practical question which may be answered by a layman of good sense with as much authority as a doctor. The weight to be properly given to the evidence touching the question depends in part upon the extent of the observations made by a witness.