Prosecution did not prove beyond a reasonable doubt that Zimmerman committed Murder in the Second Degree.
Many Prosecution witnesses bolstered Zimmerman's case.
The testimony of the Medical Examiner showing how Martin was on top of Zimmerman shows that Zimmerman was being attacked.
Trayvon Martin has a Documented record and propensity for Violence and Criminal Activity.
The Prosecution added the possibility to have Manslaughter considered because they knew they didn't prove their case. It was a hedge bet...
Zimmerman will walk... but he'll be always looking over his shoulder.
		
		
	 
You've neglected in your analysis that the jury can consider lesser manslaughter charges. I agree that the prosecution did a poor job of making a case for 2nd degree murder. Involuntary manslaughter there is a very strong case.
Point #1. Zimmerman was intructed to say in his car by police.
Point #2. Zimmerman disregarded instructions and left the car.
Point #3. Zimmerman left his car with a loaded gun.
Point #4. Zimmerman confronted Trayvon.
Point #5. Zimmerman shot Trayvon after confronting him.
To be not quilty of manslaughter Zimmermans actions must have been excusable. There are only three excuses that Zimmerman can use. Self defense not being one of them.
#1. Was the killing committed by accident or misfortune? No it wasn't. Zimmerman intentionally killed Trayvon and used a deadly weapon to do so
#2. Did the killing occurr by accident or misfortune in the heat of passion? Had not Zimmerman used a fire arm there would be an excellent argument for this excuse. He did used a fire arm so that excuse may not work.
#3. Was the killing committed by misfortune or accident if a deadly weapon is not used and the killing isn't done in a cruel and unuasuall manner? That excuse does not work as Zimmerman did kill Trayvon with a deadly weapon.
The case here is very strong for manslaughter. Since Mr. Zimmerman provoked the controntation he cannot claim self defense as an excuse for manslaughter (though for certain he can and did for murder). 
The next question if Mr. Zimmermans actions were not excusable for Florida defintion is were is actions intentional or negligent?
If the jury determines that his actions were not excusable and were intentional than he's quilty of voluntary manslaughter.
If the jury determines that his actions were not excusable and were not intentional but were negligent than he's guilty of involuntary manslaughter.
If they jury determines that is actons were excusable as defined by Florida law, then he's not guilty of manslaughter.
If the jury determines that his actions are not excusalbe but were not intentional or negligent, than he's not guilty of manslaughter.
If his is found guilty of manslaughter and because of the fact that a firearm was used, those are aggravating conditions which raise the conviction from a level 2 felony to a level 1 felony in Florida and Zimmerman would face a stiffer sentence than had a gun not been used.
So then if Mr. Zimmermans actions were not excusable by these definitions of Florida Law he could be convicted b