In any civil or criminal action or proceeding, any writing proved to the satisfaction of the judge of a court of record in an in-camera hearing to be in the handwriting of the person who is alleged to have written it, whether or not made in the ordinary course of business, may, if the court further finds that its probative value outweighs its prejudicial effect, be admitted into evidence for the purpose of making a comparison with a disputed writing on the issue of whether or not the disputed writing is genuine. The authenticity of each writing shall be finally determined by the trier of fact.