Request a clarification of "justifiable homicide" defense.

[spin]

4. Self defense is legal in all 50 states. ...

For normal self defense you can use a appropriate level of force to stop an attack but not an excessive level. For example if an aggressive individual threw a punch at you, you would have the right to use enough force to stop his attack but not kick him repeatedly in the head once he was on the ground or to beat the crap out of him.

In many states, including Florida, you can use lethal self force to stop an attack that would result in serious injury or death. Obviously the attacker has to have the means or the physical advantage to inflict such injury.

I am not an attorney but as I understand criminal law it is the governments job to prove that you broke the law beyond a reasonable doubt. It is not your job to prove your innocence.

Reasonable Doubt

A standard of proof that must be surpassed to convict an accused in a criminal proceeding.

Reasonable doubt is a standard of proof used in criminal trials. When a criminal defendant is prosecuted, the prosecutor must prove the defendant's guilt Beyond a Reasonable Doubt. If the jury—or the judge in a bench trial—has a reasonable doubt as to the defendant's guilt, the jury or judge should pronounce the defendant not guilty. Conversely, if the jurors or judge have no doubt as to the defendant's guilt, or if their only doubts are unreasonable doubts, then the prosecutor has proven the defendant's guilt beyond a reasonable doubt and the defendant should be pronounced guilty.

Reasonable doubt is the highest standard of proof used in court. In civil litigation the standard of proof is either proof by a preponderance of the evidence or proof by clear and convincing evidence. These are lower burdens of proof. A preponderance of the evidence simply means that one side has more evidence in its favor than the other, even by the smallest degree. Clear and convincing evidence is evidence that establishes a high probability that the fact sought to be proved is true. The main reason that the high proof standard of reasonable doubt is used in criminal trials is that criminal trials can result in the deprivation of a defendant's liberty or in the defendant's death, outcomes far more severe than occur in civil trials where money damages are the common remedy.

Reasonable doubt is required in criminal proceedings under the due process clause of the Fifth Amendment to the U.S. Constitution. In in re winship, 397 U.S. 358, 90 S. Ct. 1068, 25 L. Ed. 2d 368 (1970), the U.S. Supreme Court ruled that the highest standard of proof is grounded on "a fundamental value determination of our society that it is far worse to convict an innocent man than to let a guilty man go free."...emphasis added

The reasonable doubt standard is not used in every stage of a criminal prosecution. The prosecution and defense need not prove beyond a reasonable doubt that every piece of evidence offered into trial is authentic and relevant. If a prosecutor or defendant objects to a piece of evidence, the objecting party must come forward with evidence showing that the disputed evidence should be excluded from trial. Then the trial judge decides to admit or exclude it based on a preponderance of the evidence presented. A similar procedure employing a preponderance standard is used when a party challenges a variety of evidence, such as coerced confessions, illegally seized evidence, and statements extracted without the furnishing of the so-called Miranda warning.
http://legal-dictionary.thefreedictionary.com/Reasonable+Doubt

Let's assume Zimmerman approached Martin in an aggressive manner and attempted to grab him. Martin would have had the right to resist but not to sit on top of Zimmerman (once he got him on the the ground) and punch him numerous times or to drive his head into concrete.

Much will also depend to how the jurors view the incident. If they put themselves in Zimmerman's shoes and feel that they would have good reason to have feared for their life or health, then they will feel he used legitimate self defense.

The big problem in this case is that we really don't know exactly what happened that night. Without better evidence it is quite likely that Zimmerman will walk. Our legal system is far from perfect.