July 7, 2013 -- I drew a legal conclusion on "Good Morning America" Saturday that would have surprised the Dan Abrams who covered the George Zimmerman case leading up to, and shortly after, his arrest.

Now that the prosecution's case against Zimmerman is in, as a legal matter, I just don't see how a jury convicts him of second degree murder or even manslaughter in the shooting death of Trayvon Martin.

So what happened? How can an armed man who shot and killed an unarmed teen after being told by the police that he didn't need to keep following him, likely be found not guilty of those crimes?

I certainly sympathize with the anger and frustration of the Martin family and doubt that a jury will accept the entirety of George Zimmerman's account as credible. But based on the legal standard and evidence presented by prosecutors it is difficult to see how jurors find proof beyond a reasonable doubt that it wasn't self defense.

Prosecutors are at a distinct legal disadvantage.

They have the burden to prove that Zimmerman did not "reasonably believe" that the gunshot was "necessary to prevent imminent death or great bodily harm" to himself. That is no easy feat based on the evidence presented in their case. Almost every prosecution witness was called to discredit the only eyewitness who unquestionably saw everything that occurred that night, George Zimmerman.

Read More: Trayvon Martin Case: Does Zimmerman's Stand Your Ground Defense Depend on Who Started the Fight?

The essence of Zimmerman's account is basically as follows:

He spotted Martin, became suspicious, called police, was told he didn't need to follow him, was only out of his car to give the authorities an address, was jumped and then pummeled by Martin and as he was being punched and having his head knocked into the ground, Martin went for Zimmerman's firearm and Zimmerman shot him once in the chest.

The prosecution, on the other hand, called 38 witnesses to try to show: Zimmerman was a wannabe cop who regularly reported black strangers in his neighborhood; initiated and was at least at one point, on top during the encounter; that Zimmerman's injuries were minor and that many aspects of his accounts to the police and media were inconsistent and/or lies.

For a moment, lets put aside the fact that many of the prosecution witnesses seemed to help Zimmerman in one way or another.

As a legal matter, even if jurors find parts of Zimmerman's story fishy, that is not enough to convict. Even if they believe that Zimmerman initiated the altercation, and that his injuries were relatively minor, that too would be insufficient evidence to convict. Prosecutors have to effectively disprove self defense beyond a reasonable doubt. So what exactly would that mean based on the facts as we know them?

Let's take a hypothetical, but realistic, scenario whereby jurors don't believe Zimmerman when he says he wasn't following Martin (the lead detective who seemed to find Zimmerman's account credible had a problem with this part of Zimmerman's account).

Let's also assume they believe Zimmerman approached Martin and it is only because Zimmerman was tailing Trayvon Martin that a fight ensued. First of all, the fact that there was a fight at all makes a murder conviction difficult. To win a murder conviction, they have to show he had the intent to kill and did so with "depraved mind, hatred, malice, evil intent or ill will."

While prosecutors argue that Zimmerman's statements to the 911 operator about the "f------ punks" always "getting away," shows ill will, most legal analysts felt from the beginning that with a fight, a murder charge was overreaching.

Manslaughter is far more likely to create debate in that jury room (there could also be even lesser crimes they consider, where they could find him guilty of something).

Zimmerman's injuries alone -- his broken nose and cuts on the back of his head -- are objective evidence to support his account that he shot Martin as he was being pummeled.

Just as important is the testimony of neighbor John Good, who lived directly in front of the location where Martin was shot. He very precisely (but reluctantly) testified that he saw the lighter skinned man in the red jacket on the bottom of the scuffle with the darker skinned man with the darker clothing on the top in a "mixed martial arts position." He said he now believes that Trayvon Martin was on top of Zimmerman.

But wait, another witness said she thought Zimmerman was likely on top. Put aside the fact that Good's home is the closest to the incident and that her testimony didn't seem nearly as credible or definitive as Good's, that doesn't change the legal reality that one does not negate the other.

The prosecution has the burden to prove the case and so if there is reasonable doubt, the defense wins. Good's testimony in conjunction with Zimmerman's injuries are likely enough to cast reasonable doubt on the key question, which is whether Zimmerman reasonably believed he needed to shoot Martin to prevent "great bodily injury."

Of course, the jurors could also accept all or the vast majority of Zimmerman's account, making an acquittal that much easier.

What about the fact that prosecution witnesses have testified that his injuries were not that significant? While interesting (and debatable), the only relevant legal question is what was Zimmerman thinking or fearing at the time, not what already occurred.

In many self defense cases the person who shoots a fatal bullet suffers no injuries at all and instead argues he or she protected himself or herself from injury by shooting the attacker.

So wait, let's take a step back. If jurors believe Zimmerman followed Martin, maybe even racially profiled him and initiated the altercation, can Zimmerman still legally claim he needed to defend himself and walk free? Yes.

If these jurors have questions or doubts about whether, at the moment he fired the fatal shot, Zimmerman "reasonably" feared that this was the only way to stop from getting beaten further, then they have to find him not guilty.

To be clear, if we were talking about Florida's controversial Stand Your Ground Law, who initiated the encounter would be crucial and the defendant would have the burden to prove that he should not be held legally responsible for the shooting. That law, which can protect a shooter from even going to trial, wasn't designed for someone who starts a fight and then loses the fight he initiated.

Zimmerman waived a pre-trial Stand Your Ground hearing and went directly to trial (likely because his lawyers knew they would lose) and simply argued classic self-defense, which is different. Now no matter how it started, if Zimmerman shot Martin because he reasonably believed it was the only way to protect himself from "great bodily harm" then he is not guilty. That's the law.

With all of this said, juries are notoriously impossible to predict and the deliberation process can take on a life of its own, but if they follow the letter of the law, it's hard to see, based on everything we know now, how they find him guilty of either murder or even manslaughter.