The Gwinnett County Sheriff's Office says 33-yea.
Some residents in the small, largely Hispanic neighbourhood said they had no clue anything was amiss in the home until police arrived on Thursday morning.
Police said Martinez has been cooperative. The Gwinnett County Sheriff's Off. But recently, he said, she became more temperamental after her father died in Mexico and she was unable to attend the funeral.
Martinez is being held for U.S. Immigration and Customs Enforcement. She is facing 16 counts, including five counts of murder.
That child, 9-year-old Diana Romero, is hospitalized in Atlanta in serious but stable condition.
Police said Martinez called 911 to report the killings from the home the family shared outside Atlanta.
Other cases get less attention, as when a woman kills a newborn or in children's deaths blamed on neglect, said Cheryl Meyer, a psychology professor at Wright State University in OH and co-author of two books on mothers who have killed children based on about 1,000 cases during the 1990s.
According to police, Martinez went on the stabbing spree against her own family in the middle of the night, around 2 a.m. and 4 a.m. The judge advised her sharply not to perform for the cameras. "It does not matter what color you are because God loves us all", said Martinez. She later added that her lawyer will always be the people and her faith.
She'll be back before the court for first appearance on July 20.
As Judge Thorpe listed the charges against her - five counts of malice murder, five counts of murder and six counts of aggravated assault - Martinez smiled, shook her head and wagged her finger at him.
She refused an attorney and even smiled at the news cameras there, giving a thumbs up.
Gwinnett County Magistrate Judge Michael Thorpe advised her to stop performing for the cameras.
The mother accused of fatally stabbing four of her children and their father appeared to pray, smiled, and gave a thumbs-up to cameras during a freakish court appearance Friday in Georgia.
Isabel Martinez is accused of murdering her husband Martin Romero (pictured), along with four of their children.
Martinez is also charged with stabbing her fifth child, a little girl, who was airlifted to a hospital and expected to remain hospitalized for two or three weeks, according to a GoFund Me page set up by family members.