Lacey Spears from Kentucky appears on charges of depraved murder and manslaughter, after her 5-year-old son died with unexplained excessive levels of sodium in his stomach.
The 26-year-old pleaded not guilty to the charges on Tuesday and is being held without bail.
Prosecution lawyer Doreen Lloyd said that the young boy's death was ruled a homicide, and that the accused poisoned her son over a long period of time. Garnett died from excessive swelling of the brain in January this year.
In early January, Lacey admitted her son Garnett to Nyack Hospital in Rockland County, after reporting he was having seizures and developed a fever.
But two days later, with no medical explanation, Garnett's sodium levels rose to dangerous levels and he was transferred to another hospital. At the time of the sodium rise, Lacey was sharing a hospital room with her son.
Hospital workers became suspicious of the mother after they registered Garnet's dangerously high salt levels, and called children's services - who then launched an investigation.
A neighbour of the family, who did not wish to be named, said that as Garnett was dying, Lacey asked her to go to her home and dispose of one of her son's feeding bags. Initially following her friend's instruction, she later realised her mistake and turned the evidence over to police.
Investigators believe that Lacey may be suffering from Munchhausen by proxy, in which the person intentionally hurts their child to get attention.