How to evaluate the impeachment witnesses' testimonies?

Since the impeachment proceedings are primarily governed by the Revised Rules of Court, as amended, it is important that senator-judges, especially the majority who are not lawyers, may take note of the following cardinal rules on evaluating the quality and admissibility of evidence

The first cardinal rule is the one on the principle of credibility. Is the witness credible, is his story believable. In the language of former associate justice and former ombudsman Conchita Carpio Morales, for a testimony to be admissible, it must come from a credible source and the story is credible by itself. The believability of the story refers to the intrinsic admissibility. The credibility of the witness refers to the extrinsic credibility. In the language of laymen, it is not just the song but also the singer.

Under Rules 130, Section 21 of the Rules on Evidence, a witness is competent to testify if he or she is able to perceive facts (either by sight, hearing, smell, touch, and taste), and having perceived can communicate to the court what were the objects of his perception. Second, the rules require personal knowledge. The witness himself was the one who perceived and that he is precisely communicating the same object of his perception. That means that rumors, speculations, beliefs, opinions, and secondhand information are not admissible as basis for a finding of fact.

As acceptable indicators of credibility, the following are accepted by the Rules of evidence: facial expressions, body language, tone of voice, hesitations, spontaneity of answers as well as overall demeanor of the witness while giving testimony. They are generally accepted as badges of credibility or lack thereof. That is why the vice president should appear and testify so that the senator-judges can see her demeanor and her overall behavior. That shall serve as an impeccable indicia of her credibility.

When is a testimony credible in itself? To answer that question, the following specific queries should be addressed: First, does the story make sense? Is it consistent with how normal human persons behave under the same factual circumstances? Is the story being supported by surrounding circumstances? The senator-judges should be very alert and discerning. They should not be occupying themselves with extraneous matters because of a very close scrutiny of the movements, demeanor, and body language of all witnesses, most especially the vice president herself who is the respondent.

What happens when the same witness makes contradictory statements at one time or another, would it affect the credibility of such a witness? And would it discredit the whole testimony itself based on the Latin maxim "Falsus in uno, falsus in omnibus?” The force of jurisprudence says that if the contradictions pertain to material facts, the answer to the question is yes. It will affect the credibility of the witness and may discredit both testimonies that contradict each other.

However, minor contradictions on unessential matters may be attributed to the frailty of human memory. Some testimonies may be a result of stress and surges of emotions under very difficult circumstances. Minor discrepancies may not necessarily impair credibility when the essential facts remain constant and consistent. It could even be appreciated as a badge of truthfulness and spontaneity and is not being rehearsed.

Based on the foregoing, you, dear readers, may be able to assess the credibility of the impeachment witnesses by yourselves. I hope the non-lawyers among the senators would also exercise some degree of diligence in asking their respective legal staff to provide them with the required technical information on these matters.