The wife of George Zimmerman, a Florida neighbourhood watch leader acquitted in July of murdering the unarmed teenager Trayvon Martin, is filing for divorce, her lawyer said on Thursday.

Shellie Zimmerman, 26, will present documents to court officials on Friday in Florida's Seminole county, according to attorney Kelly Sims. The couple had been married for six years.

George Zimmerman's brother, Robert, appeared to confirm the news in a tweet on Thursday evening. "According to Shellie's atty Kelly Sims – Shellie is preparing to file 4 divorce. Doc have not yet been filed in Seminole Cty. Pray 4 them," he wrote.

Shellie Zimmerman was sentenced to 12 months of probation last month after she admitted lying to a judge about their finances during her husband's bail hearing in June 2012. She said in an interview after her conviction for perjury that she felt he had "beaten down her self-esteem" and that she was no longer sure if she wanted to remain married.

The announcement came on the same day that it was revealed that George Zimmerman, 29, received a speeding ticket after he was stopped earlier this week by police in Lake Mary, close to the central Florida town of Sanford where he shot and killed Martin, 17, in a confrontation at his gated housing community in February last year.

A jury of six women cleared him of second-degree murder after a three-week trial that ended in July, the verdict sparking demonstrations in many cities across the US. In an interview last week, Shellie Zimmerman said that the couple had received numerous death threats and had "lived like gypsies" in the months between the shooting and her husband's trial, spending many nights in a mobile home hidden in woodland.

She also revealed that she was not at the couple's home on the night of the shooting, having left the house the day before after a fight with her husband. When the interviewer, Good Morning America's Christi O'Connor, asked her if George Zimmerman had a volatile temper, she replied: "I'm not going to answer that."

Further tension between the couple was indicated by George Zimmerman's decision not to attend his wife's 28 August perjury hearing at the same Sanford courthouse in which he was acquitted more than a month previously. She said she felt "let down" by his absence after she attended every day of his murder trial.

In a plea bargain brokered by prosecutors, Shellie Zimmerman admitted to a misdemeanour charge of perjury for telling a judge in June last year that the couple was virtually penniless, despite having control of more than $150,000 (£96,000) in public donations to his defence fund that had been raised online.

The deal, which allowed her to escape a felony perjury conviction and possible five-year jail term, also required her to write a letter of apology to Judge Kenneth Lester, who was overseeing her husband's case at the time.

"I was aware that what I was saying was not true, and chose to take a path that I now regret with all my heart," she wrote.

The ABC interview gave further glimpses of how her opinion of her husband had changed over time. She said she felt he was insensitive when he visited the Florida gun factory of Kel-Tec, the manufacturers of the 9mm pistol he used to shoot Martin in the chest, and was photographed smiling and shaking the hand of an employee.

A spokesman for George Zimmerman's lawyer, Mark O'Mara, said the gun factory visit, six weeks after his acquittal, "was not part of our public relations plan".

Zimmerman's speeding ticket this week was the second time he had been stopped by police since the trial. In July, an officer in Forney, Texas, let him off with a warning after pulling him over. Zimmerman told the officer that he had a legally held weapon in the glove compartment.