Let's suppose those assumed paths were not known. What we know is that Zimmerman's car was a block away from the crime scene. We know that Zimmerman followed Trayvon. We also know that Trayvon's girlfriend's house was just a few doors down and that he was unarmed.
What we have is a man who followed (if not cut off) his target, while being armed, and killed him. We know for a fact that Zimmerman shot Trayvon. We know for a fact that Trayvon was unarmed.
What should this tell you? Prosecutors should have pressed charges and let Zimmerman prove his defense to a jury of his peers. That is the way this country, and justice system, was designed.