Marissa Alexander no longer wears an ankle monitor. She is now free to go to the park and play basketball with her children in her Jacksonville, Fla., neighborhood. She can ride a bicycle and stroll on the beach, which she dreamed about in prison.

“I didn’t carry an umbrella when I first got home,” she said, “because I wanted to feel the rain drops on my skin.”

Ms. Alexander, 36, spent almost a half-dozen years either locked in prison or confined to her house after she was convicted of aggravated assault charges in 2012 for firing a warning shot at her husband, who she said had abused her. According to her account in court documents, he had threatened her nine days after she gave birth to their daughter.

Ms. Alexander was finally freed on Jan. 27. She plans to take up the fight for domestic abuse victims and push for a change in what advocates have called the uneven application of Florida’s Stand Your Ground law. She will advocate amending the law in order to take the burden of proof off defendants who have to demonstrate in pretrial hearings that they acted in self-defense and deserve immunity from trial.