There is only one charge against Zimmerman: murder in the second degree. There are no lesser charges. If the prosecution has failed to provide sufficient evidence of depraved mind then the judge can issue a directed verdict of acquittal. The prosecution cannot reduce the charge once the trial has begun.
Manslaughter is a necessarily inlcuded lesser offense, and MUST be given to the jury.
Interesting because all the pundits keep talking that the jury could find him guilty on Manslaughter. But as I search the internet I can not find any charges on Manslaughter. I read articles and forums from 2012 and even supporters of 2nd degrees argued against Manslaughter. I think the line between certain types of Manslaughter and self defense is so thin that no prosecutor would have brought it to a jury.
After the prosecution rests, the judge should acquit. Zimmerman doesn't need to take the stand because the prosecution played interviews of Zimmerman that were not self incriminating. Why be cross-examined now?