This poor 12-year-old girl, Kaitlyn Yozviak, died from suffering from a fatal heart attack and anemia. She had severe lice infestation –on and off- for 3 years, which lowered her blood iron levels and possibly was the reason for her going into cardiac arrest. Her parents were arrested for this because it was seen as 'second-degree murder.'
Mary Katherine "Katie" Horton, 37, (mother) and Joey Yozviak, 38, (father) have also been charged with second degree-degree child cruelty.
During the Georgia Bureau's special investigation, it was revealed that when Kaitlyn died, she saw that Kaitlyn had one of the largest lice infestations they had ever seen.

She Had This Lice Problem For Three Years
The officer said that the girl had this lice infestation for 3 years. That caused her to have low blood iron levels and thus lead to cardiac arrest and the girl's death.
After sufficient evidence was collected against the parents, they were charged with second-degree murder.

Mother Revealed Kaitlyn Had Not Taken A Bath For A Week And A Half Before She Died
Mary Katherine, Kaitlyn's mother, found Kaitlyn unresponsive on August 26 and called 911 right away. Kaitlyn got rushed to Milledgeville Hospital, where the doctors pronounced her as dead.

Kaitlyn's Mattress And Other Belongings Covered In Vermin
After Kaitlyn was pronounced dead, the authorities went to the girl's house to do an investigation and found that Kaitlyn's mattress, stuffed animals, and other furniture were covered in vermin.

The parents were sent to jail because they neglected the fact that Kaitlyn was suffering from this severe lice infestation. They did nothing about it, thus being seen as poor parenting. So, they were charged with 2 counts:
Second-degree murder and second-degree child cruelty.