In 13 Reasons Why, Hannah Baker's tapes receive some suspicion of truth, accuracy or completeness. Some, like Bryce, asked questions like 'Who's gonna believe a dead girl?' while others said 'Why would a dead girl lie?'. The thing is: who isn't gonna believe a dead girl by the dying declaration rationale?
In law there is the concept of a Dying Declaration, which attributes higher truth value to testimonies made by a dying person:
The rationale, accurate or not, is that someone who is dying or believes death to be imminent would have less incentive to fabricate testimony, and as such, the hearsay statement carries with it some reliability.
Forget the legal concept a bit because I'm not so interested in admissibility of the tapes and focus more on its rationale and hence the credibility of the tapes.
So why aren't Hannah Baker's tapes assumed to be (likely) true? Why is there such a reluctance by the characters to believe her tapes? I suspect the dying declaration rationale might be N/A due either to certain events or sayings in the show that I may have overlooked or to certain legal aspects like suicide not being part of the dying declaration. In the Wiki article, I didn't see anything in the US section about suicide. I have a feeling it's inferred from somewhere that suicide doesn't count.