Testimony of personal knowledge trumps mere denial every time someone said. Right? Wrong! Testimony of personal knowledge is just testimony. It is not knowledge. It is not fact on its face.
In legal procedure, every positive allegation of personal knowledge is sufficiently answered by mere denial without anything more. Answers to Complaints must read “I specifically deny” such and such allegation in the complaint and that is enough to trump the allegation; no need of proof to back the denial because in logic you cannot prove a negative.
True, Holmes said “the life of the law is not logic but experience.” But logic is the distillation of experience; it sharpens the blunt edge of experience to cut deeper into the lie to reveal what is beneath if anything at all.
Mere denial shifts the entire burden of proof to the one alleging personal knowledge and puts her to the proof of her truthfulness. If she fails the proof, she is mendacious which is the $10 word for a liar.
In law, to accuse someone of something that you personally know begs the question if you did not make it all up; if you did not weave a fabric of lies.
I was with Pepe Diokno when he instructed the judge in the case of the Haruta Letter that a consistent testimony must be consistently a lie; no one remembers so much so accurately.
In short, personal knowledge is merely a ground for the admissibility of evidence that it is not hearsay but that is all. It is not proof of its veracity. Even worse, an accusation based upon a claim of personal knowledge exclusive to the accuser invites suspicion of complete fabrication. That’s not Blackstone or Joseph Storey; even better, that’s me.