There are no other characters introduced in this arc, unless you count the other police officers, so unless it's a gag reveal (like "the culprit wouldn't admit to that!") then there's really no other choice. Honestly, if they do just point out the murderer at the beggining of the next chapter, then I'm officially calling BS. There are no solid clues shown here at all. The other arc at least had the missing ring on the culprit's hand (though the premise of a poison paralyzing and killing someone instantly is ridiculous and shows lack of reserach), this time nothing points to anyone at all.
There are bits that seem like clues, but ultimately, they're dead ends, examples:
- The statue is supposed to be the work of a graduate student of the victim. It might have been Suzuka before he became a teacher, but that's pure conjecture, we don't even know how old he is, much less if he knew the victim before his current job.
- The lipstick bit suggests that she was either going out or waiting for someone, but it could have just as easily been planted by the prepetrator.
- I was thinking the Yokohama pictures would be hiding some meaningful detail, like something pointing to it not really being Yokohama. It seems to be the opposite - the tower shown is a known landmark there. I also considered that maybe he'd be in different clothes between the pictures (due to the paint fiasco), but no, nothing obvious comes up. The pictures seem to provide a solid alibi if anything.
Since the time of death is only a rough estimate, she could have been murdered before the event. If we assume she was also supposed to be at the training event (again, no info), that would explain the lipstick, support this hypothesis and kind of point to Suzuka, since her being still at home would mean that he too wouldn't be expected there yet. However, we're not told at which hour the mentioned staff training started or when was the 30 min break, so this is again just a baseless conjecture.
There's also no real motive, unless we assume that the "young teacher" involved in the affair was Suzuka himself and he wanted to get her for messing it up. It still doesn't really make sense, since he pointed the finger at his would be lover... Also, he'd be a fool to even mention it without admiting his role in it, it's gonna come out anyway if it's such a well known incident.
So yeah, looks like the author has chosen the Kindaichi approach, where the manga simply does not show the crucial elements to the viewer, so that the conclusion is "shocking". Either that, or it's going to be an asspull, where the culprit has some flat out crazy "artistic vision" and that's why he's done it...