Belnap wrote that the woman had an "unconscious lapse of awareness" when she left her child in the car which is very different from making a conscious choice to leave the infant there.
"The evidence," Belnap added, "shows that April was a loving, thoughtful caregiver who was operating under lack of sleep, changed routine, and stress."
Belnap detailed the events leading to the death as follows:
During the week leading up to Aug. 1, Skyah had been teething and neither mother nor child had been getting much sleep.
April also had not been feeling well for several days and the night before, and she and her daughter woke up in the early hours of the night and played together for several hours.
The day of Aug. 1, the mother had a standing nail appointment with a neighbor. Her usual routine was to take her two boys, ages 3 and 5, to a baby sitter and leave Skyah with her sister, who was living in the home.
But that day there was no one to watch Skyah, so shortly after 10:30 a.m., the mother put her in a rear-facing car seat in the back seat of the car, along with the boys, and headed to the baby sitter's home, who lives about five minutes away.
After dropping off the boys, the mother drove home, but had to park on an adjacent street because of street construction in front of her home.
As she exited her car, her attention was diverted by a construction worker, who said something to her about the parking.
The mother then walked around the front of the car and headed home.
She hurried inside because she needed to use the bathroom, then heard her neighbor arrive for the nail appointment.
The mother left the bathroom and went directly to the room where she does nails and where the neighbor was waiting.
The appointment lasted about an hour.
"April said the entire time she was doing the neighbor's nails, April believed that Skyah was downstairs sleeping in her crib because that was her normal routine," Belnap wrote.
Because the mother had not heard Skyah cry or make any noise, she believed the child was still sleeping. So when the nail appointment ended, the mother decided to leave Skyah sleeping while she picked up her boys.
When she arrived at the sitter's house, she left the car running and ran inside to get her sons. She told them to hurry because Skyah was sleeping at home.
"As April was loading the boys into the car," Belnap wrote, "she saw Skyah in the car seat and started to scream."
The mother took Skyah and ran into the neighbor's house and yelled for the baby sitter to call 911.
Skyah was pronounced dead at the hospital.
State Medical Examiner Todd Grey ruled that the cause of the infant's death was hyperthermia and the manner of death was accidental.
The temperature at the nearest weather substation was 83.9 degrees at 11 a.m. and 89.6 degree at 1 p.m., according to Belnap's letter.
Investigators ruled out any use of prescription drugs or illegal drugs. Neither the mother nor any immediate family members have any prior history of child abuse or neglect, according to Belnap.
Prosecutors consulted an expert in inadvertent memory lapses who has studied hundreds of cases of parents who leave children in hot cars.
David Diamond said such a memory lapse "is not an act of negligence; rather it is an unconscious result of converging circumstances triggering the habit-based portion of the brain to overcome the thought-based portion of the brain."
After reviewing the case of Skyah's death, Diamond expressed the opinion that "this is a classic case of lapse of awareness and that there was no volitional wrongdoing by April," according to Belnap's letter.