Teenager has night shift at a pharmacy (like Boots) and he works at a Photo lab. He rides his cycle there, he crashes and is left with the handle bars and one wheel, he says "this is not my day". He then walks to the front of the store door, holding what is left of his bike. He drops the keys whilst trying to enter the store, he says "this is not my day". He then begins processing photos, in the photolab. He realises a photo of a dead body laying on a floor with blood coming from it's head. He says, "this is not my day". He panics and, holding the photo, runs out of the photolab, tripping over what's left of his bike, doing a flip, and landing on the store floor, holding the picture. The camera slowly zooms out of the picture in his hand of the 'corpse on the floor' to the teenagers body on the store floor.
Wasn't sure how to go about doing a 'whodunit?' as it requires me to try and come up with the perfect murder, which is very difficult to do. Although you see it time and time again on detective shows like 'Monk' it is still very difficult to do. I remember seeing a 'behind the scenes' thing of 'Monk' on how the writers create murders but this is not with me at the moment, and I couldn't find it on YouTube.
I was thinking something along the lines of, the forensics lab as suggested by Phil, and have their be the 'hair' from 3 possible suspects.
Detectives questions the 3 suspects, but get nothing.
Something gives the detectives a 'big break', maybe one gets angry, throws the unicycle (evidence) against a wall, and something falls from it?
Then this 'big break' allows them to question a suspect again, and they resolve the case?
I'm really struggling with surfacing this idea, maybe this is what 'Writer's block' feels like if that is such a thing, but on a serious level, I don't know, I'm seriously considering my 'Boots' photo lab idea.