So, I think the disorderly crime scene is indicative of a violent crime. I think we can rule out anything subtle and go for the obviously violent weapons. I imagine there was a struggle, a bit of a fight, and the attacker got the upper hand.
I think the obvious weapons are:
Bite and Tear?
This means almost all of us are still suspects.
Evidence that matches the crime scene is less so.
Take out food (A stretch, but possible)
Surveillance Camera(lots of those in public buildings)
Pocket Watch (Easily dropped.... but also easily dropped pretty much ANYWHERE)
Gift (common reason to be at a gift store)
Exam Paper (kind of a stretch as it's not a library, but you never know who went to Borders to study)
Button (Same as watch, easily lost while attacking the victim, but also easily lost ANYWHERE)
Mirror (can be a dropped hand mirror, a broken compact, or just a mirror in the bathroom or situated as decoration in a bookstore)
Cassette Tape (Because our murdered is from the 90s? Books on tape and what not)
Watch (Same as watch and button above)
Tea Leaves... (It's a stretch, but book stores do sell odds and ends, and maybe it was buy a book on divination)
Note book and candy (both items sold at bookstores)
Hair (Same as watches and button)
Hat (Same as watches and button)
Juice.. (could be sold at a book store. Another one that is a bit of a stretch)
Okay, so I feel like there are some people we can rule out.
ME! Cause I know I didn't do it, lol.
Remiel, doesn't seem to have a weapon that would lead to serious injury, more like blood loss, or other causes of death. His evidence is kinda hit or miss, too.
Christa, Her evidence just doesn't fit and her most seriously injuring attack is a punch. Bracelet could fit ANYWHERE, not sure I caught that one above, but it's another watch/buttons/hair/hat
Rapt, great choice of injuring weapons, but the evidence doesn't seem to be there. Cassette tape seems like a stretch.
Ryven, Can't imagine bringing dumbells to the bookstore, and otherwise he's lacking in good weapons. Evidence is also kinda weak.
And for the people who look the most guilty...
ME! Seriously, I look guilty as hell. I've got good weapons and some damning evidence. I am innocent, though.
Night Owl, good attacks and a few peices of evidence that fit the scene. Gifts and Cameras and watches oh my.
MP, looks about as guilty as I do, but I'd say my notebook is more common in a book store than her exam paper. Let's remember it's a store to buy books, and not a library.
Rel, has the bat, my favorite for a weapon used to cause serious injury. I would only favor it over the wrench because of the reach it gives, electric current also provides some serious injury. Between the tool box and the oil paining, the evidence is kinda lacking. Oil paintings could be for sale at a book store? Fancy fancy book store, ooh la la.
Yugi has some good weapons, bite and tear would be some serious damage, same with the scissors. Evidence is sort of lacking, though.
Phoenix, Has a cleaver, has hair and hat.. but that evidence is so broad.