Martin would have plenty of time, assuming he wasn’t lost at the time.
Probably what will hinge on intent is what can be shown as what happened just prior to the scuffle between the two.
If it can be shown that Zimmerman caught up with Martin, that would show Martin was still trying to retreat. This would make Zimmerman the likely aggressor, removing any claims of self defense. If,however, it can be shown that Martin had to doubleback, then it would support Zimmerman’s claim for self defense.
The initial contact is irrelevant unless you can show that the actions taken by Martin was an appropriate response. Considering that Martin was on top of Zimmerman and beating him about the head, which is what the evidence and eyewitness testimony show, your burden to show justification is pretty heavy.