A good mystery provides enough clues to work out the criminal without just handing you the answer. It's disappointing how easy the first mystery is, but I see this as an introduction to the game at the easiest difficulty. There are clues to push you away from the correct answer, but some clues hold more power than others. The debate should take all the clues into account before accusing anyone of the murder.
The most important clue is Maizono's dying message. It reveals who is most likely the killer using the numbers 11037. Instead of just writing their name, it is written in numbers as to not seem too obvious. It was probably to prevent it being erased if the killer saw the numbers being written. All the evidence could be planted including the dying message, but these are the only clues that can be linked to someone in particular.