Bill Clinton has stepped into the furore over the shooting of Trayvon Martin by calling for a reappraisal of Florida's controversial "stand your ground" law.
The former US president said the death of the unarmed teenager at the hands of a neighbourhood watch leader was an "incredible personal tragedy" that resulted from "a breathtaking expansion" of America's concealed weapons laws over the last decade and a half.
His comments came as ABC News released enhanced video footage that it claims shows Martin's killer, George Zimmerman, with gashes or welts on his head. Zimmerman's attorny said his client would turn himself in to authorities in the event he is charged.
Clinton said that the "stand your ground" law, under which Zimmerman avoided charges for the incident on 26 February by claiming he was acting in self-defence, created more challenges for investigators.
"It's going to be almost impossible to prove what was in someone's mind when a certain thing happened," he said in an interview with ABC.
"The law is going to create real problems because anyone can basically be a part of a neighbourhood watch where they have a concealed weapon, whether they had proper law enforcement training or not, and whether they've had any experience in conflict situations with people or not.
"People have always had a right to have a handgun in their home, to protect their homes, then we've seen this breathtaking expansion of concealed weapons laws. I hope this will lead to a reappraisal of the 'stand your ground' laws, that the truth will come out and that the tragedy of this young man's loss will not be in vain."
Since the measure was passed into law by then Florida governor Jeb Bush in 2005 it has been cited in at least 140 cases, according to the Tampa Bay Times. It removed a citizen's duty to retreat from a situation in which he or she perceived their life or safety to be in jeopardy and allowed instead for use of deadly force.
In another development on Monday, Zimmerman's defense attorney Craig Sonner said his client would continue to co-operate with the authorities.
"If he's charged, he will be arrested and he will turn himself in. However it goes, he's not hiding from the authorities. If he is asked, he will turn himself in. There's not going to be a manhunt or anything like that," Sonner told Reuters in a telephone interview.
Earlier, ABC's Good Morning America broadcast a video of Zimmerman's arrival at Sanford police station soon after the shooting, which it says was digitally enhanced and shows injuries to his head.
Zimmerman told police that Martin broke his nose with a single punch and slammed the back of his head on to a concrete pavement during their fight, a claim denounced by Martin's supporters last when the leaked original video showed no apparent signs of injury.
ABC reporter Matt Gutman said that the enhanced footage, produced by a company run by a former FBI investigator, shows "what appear to be a pair of gashes or welts on George Zimmerman's head".
In today's other developments, lawyers for Martin's family said they would file a complaint with the US department of justice that a Florida state attorney turned down a police request for a warrant for Zimmerman's arrest.
Attorney Ben Crump said he wanted an ongoing federal investigation to look at possible interference by Norm Wolfinger into the handling of the police inquiry. Documents from the night of the incident indicate that police believed there was possible cause for at least a manslaughter charge.
Wolfinger has since stepped down from the case. Florida governor Rick Scott appointed a special prosecutor, state attorney Angela Corey, to determine if Zimmerman, 28, should be charged.
At a rally in Miami, Martin's hometown, on Sunday, civil rights leaders Al Sharpton and Jesse Jackson appeared alongside his parents, Sybrina Fulton and Tracy Martin, to repeat calls for an arrest.
It followed a similar gathering in Sanford the day before, organised by the National Association for the Advancement of Colored People.
"This case was mishandled from the start. We're marching to ensure justice avails," said Turner Clayton, president of the NAACP's Seminole County chapter.