The Trayvon Martin case may have brought renewed focus on new "stand your ground" self-defense laws around the country, but the defendant in the case, George Zimmerman, said Tuesday he may not use the law in his own defense after all.

In a move that bewildered prosecutors, defense attorney Mark O'Mara cancelled an April 20 "stand your ground hearing," claiming a time crunch in preparing for a June 10 jury trial in the second-degree murder case. If able to provide clear and convincing evidence of legally standing one's ground against an attack, a defendant in Florida walks free and is granted immunity from civil liabilities.

Police released Mr. Zimmerman without charges after the volunteer neighborhood watchman shot 17-year-old Trayvon Martin just over a year ago. Sanford, Fla., police cited Florida's landmark 2005 “stand your ground law,” which nullifies any imperative for a potential crime victim to try to escape or retreat before using deadly force against an attacker.

Zimmerman says he thought Trayvon looked suspicious, and that the two fought after he approached the boy. Zimmerman says he didn't know Trayvon was a child.

According to Zimmerman, Trayvon knocked him to the ground, straddled him, knocked his head against the pavement, and punched him wildly to a point where Zimmerman feared for his life. Then Zimmerman pulled out a pistol and shot Trayvon square in the chest, killing him.

Forty days later, after nationwide protests, a special prosecutor arrested and charged Zimmerman with second-degree murder, saying he illegally confronted an unarmed child for no reason, provoked a confrontation, then killed the boy without cause.

The case gained nationwide notoriety because of suspicions of institutional police biases against blacks, especially young black men. It also became a waypoint in a national debate about an ascendant US gun culture that has led to the loosening of gun laws and to the expansion of "no duty to retreat" self-defense laws that apply both to conduct in the home as well as in public areas like sidewalks and parks.

Some legal experts following the case, however, were not surprised at the defense's decision to forego a "stand your ground" hearing, given normal legal maneuvering in a high-profile murder case.

One argument goes that Zimmerman's ultimate claim may not be "stand your ground" at all, since he technically was on the ground and unable to retreat any further at the moment he shot Trayvon. In that scenario, he could claim self-defense under pre-"stand your ground" laws.

A more likely scenario, says University of Florida law professor Bob Dekle, is that Mr. O'Mara doesn't want to go through a bench mini-trial and possibly tip off the prosecution about its strategy should the "stand your ground" plea fail.

"If you're not 100 percent sure you're going to win the 'stand your ground' hearing, you just end up telling the state what your defense is and you've got nothing with which to surprise the state at trial," says Professor Dekle. "What you want to do at trial is catch the state with their britches down."

Several new developments suggest that Zimmerman's defense attorneys are having some success finding information that could raise doubts among jurors about the state's version of events. For one, the defense has been digging furiously, with the judge's permission, into Trayvon's social media history, which may present a more complex, edgier picture of the youth.

Also on Tuesday, a key witness for the prosecution was caught in a second apparent lie amid probing by the defense. A woman who says she was on the phone with Trayvon as Zimmerman pursued him originally gave her age as 16, though she was really 18. And she also said she missed Trayvon's funeral because of a hospital stay, which wasn't true.

Prosecutors were put in the awkward position of having to explain that situation as reporters asked questions about whether they would charge the woman with perjury, as prosecutors did Zimmerman's wife, Shellie Zimmerman, after she allegedly lied about the couple's finances during a bond hearing last year.