Interesting point there, sgl. However, without consciousness, Persephone is unable to take blame, so the question we have to answer first is that: Is Persephone conscious and self-aware? Currently, signs point overwhelmingly to “No”. A being that could reason beyond how it was initially programmed could have inferred that Hina wanted the door open for Travis in Chapter 1 despite not using a keyword, and would have given everyone more detailed answers than “ERROR” when it was asked about the body in Chapters 1 and 2. Plus, the programming behind a self-aware artificial intelligence would be extremely complicated, and it is extremely unlikely that Robbie would have the knowledge required to even work with one, never mind be “the best technician the ship has had in its 600-year trip.” (Character Bios, Robbie) However, Persephone seems to be able to selectively increase the access she gives to certain individuals (READ: ROBBIE), which is probably why the question of blame is coming up. However, Robbie could have, in theory, given himself more privileges through personal backdoors, or backdoors left by his predecessors.
However, we also must consider the possibility that I may be wrong, and that Persephone is indeed self aware and conscious. In that case, it actually is really simple to justify Persephone’s actions: she wanted to do those things. Mind, Persephone absolutely only responds to commands given after the keyword “Persephone” because Persephone understands the principles of good user interface (THAT WAS INTENTIONAL TRAVIS OR WOULD YOU RATHER HER FLOOD THE ENTIRE SHIP WITH DEADLY NEUROTOXIN WHILE YOU ARE DISCUSSING THE SCIENTIFIC ACCURACY OF PORTAL), but the rest of those things she could have done because she genuinely wanted to.
Either way, I am frightened by what would be implied if Persephone was guilty in either case. If Persephone was sentient, it would mean that the entity charged with the safety of the entire population of the ship would be subject to the whims of base emotions desires, and opinions, which could potentially lead to some extremely frightening scenarios. If Persephone isn’t sentient, but she intentionally allowed or caused this murder in some way, that means that someone programmed her to do this, possibly the original creators. They would have had an ulterior motive to all this, and the code they installed would probably still be running unbeknownst to the crew, because the malicious individual would be sleeping off the rest of the journey to Tau Ceti Prime. And while Persephone being sentient and hating everybody is a scary prospect, I think having malicious code inside her would be far worse.
So basically it comes down to this: We don’t want Persephone to be guilty, because if she is everyone is absolutely screwed, either by a snippet of malicious code or Persephone’s bad attitude.