in arriving at these conclusions, the city prosecutor already delved into the merits of the respondents’ defense.  This is contrary to the well-settled rule that the validity and merits of a party’s defense and accusation, as well as admissibility of testimonies and evidence, are better ventilated during trial proper than at the preliminary investigation level.^⁠7  The allegations adduced by the prosecution will be put to test in a full-blown trial in which evidence shall be analyzed, weighed, given credence or disproved.^⁠8  The preliminary investigation is not the occasion for the full and exhaustive display of the parties’ evidence^⁠9.  Simply put, in determining probable cause, the average man weighs facts and circumstances without resorting to the rules of evidence that, as a rule, is outside his technical knowledge.^⁠10 

That the findings of the city prosecutor should be ventilated in a full-blown trial is highlighted by the reality that the authenticity of a questioned signature cannot be determined solely upon its general characteristics, or its  similarities or dissimilarities with the genuine signature^⁠11.  The duty to determine the authenticity of a signature rests on the judge who must conduct an independent examination of the signature itself in order to arrive at a reasonable conclusion as to its authenticity.  Thus, Section 22 of Rule 132 of the Rules of Court explicitly authorizes the court, by itself, to make a comparison of the disputed handwriting “with writings admitted or treated as genuine by the party against whom the evidence is offered, or proved to be genuine.”^⁠12 

Read in this light, the respondents’ defense that there are striking similarities in the specimen signatures they submitted and those of the questioned deeds is  a matter of evidence whose consideration is proper only in a full-blown trial.  In that proper forum, the respondents can present evidence to prove their defense and controvert the questioned documents report; they can raise as issue the alleged irregularities in the conduct of the examination.