*SPOILER* PLOT DEVICE - JP convicted without proper evidence?
It's unclear.
1. The police does not know the motive.
2. He is not linked to the crime scene.
3. Zero witness, whatsoever.
4. His guilt can be easily proven false. Many people knew the girl bled from her nose, which substantiates his explanation for the ONLY evidence against him. He could also very easily prove he was going out with her, everyone seemed to know about that.
This looked like a convenient plot device to me. Otherwise a good movie. Dark though !