Heya,
cheers. I guess the short version is that there is indeed a "hidden rule" of at least one truth that was pretty badly communicated (i.e. not at all). But I would also say that I didn't really intend to make a pure deduction game with this demo, but rather a "mostly deduction but some induction too". This is more closely oriented at a classical mystery, where you can't really make conclusions with a 100% certainty, but rather have to guess the most probable outcome. In this example, you could say that it's hard to tell which one of the two logical solutions is the most probable one. Either both lie or both are telling the truth. In my head, it is slightly more probable that the murderer is telling the truth, which leads to the capture than the witness lying and making themselves suspicious. But of course with this level of abstraction, what do things like "murderer" or "witness" even mean. I guess that the concept of lying was only introduced after this second round, so I guess that definitely also influenced what is happening there.
Anyway thanks for the comment, there will definitely be more thought behind the next iteration!