Fortunately, Zimmerman's story is unraveling.
With the welcome news late Monday that the U.S. Justice Department will open a civil-rights investigation - along with a Florida county grand jury probe - more and more troubling details of the Feb. 26 shooting of Martin are coming to light.
There's a 911 call in which Zimmerman was told by police to back off, rather than approach the teen he suspected of planning a break-in. He ignored the directive. Moments later, he shot Martin.
On the 911 recording, Zimmerman is heard to utter a racial epithet and express frustration that criminals "always get away."
Most damaging of all to Zimmerman's claim that he was attacked, without anyone as a witness, is a report that a clearly worried Martin phoned his girlfriend to tell her he was being stalked.
The full investigation that's warranted also must examine why Sanford police failed to test Zimmerman's sobriety. Was there racial bias in how police approached the case?
Even as this incident gets intense scrutiny, there's still all the self-defense statutes that could shield other reckless shooters. It's a problem that could come home to roost in any Pennsylvania community - especially in Philadelphia, where gun violence is epidemic in some neighborhoods.
While long recognized as a valid defense when someone is attacked inside his home, these expanded "castle doctrine" laws, as they're known, now cover virtually every setting. With states also being pushed by the National Rifle Association to loosen rules on carrying weapons, and gun owners emboldened by expanded self-defense rules, the risk for violent confrontations grows.
So a road-rage incident or tavern quarrel that might have led to a scuffle may now erupt in gunfire, with the last man standing claiming a right to shoot because he felt threatened. Even more perverse, drug dealers and other criminals settling scores can claim a legal right to replay the O.K. Corral.
In Harrisburg, both Gov. Corbett and the majority-holding Republican lawmakers knew the risks when they expanded the state's "castle" doctrine last year. With the Florida case, they have more than enough evidence that the law should be repealed.