A father is charged in the death of Sterling Koehn, who was in the same maggot-infested diaper for nine to 14 days when EMTs were called to the home: https://t.co/T0PumVgPv1 pic.twitter.com/xwiKEa0Ocf — 48 Hours (@48hours) November 5, 2018

Sterling Daniel Koehn was found dead on Aug. 30, 2017, at his parents' Alta Vista apartment. According to the medical examiner, evidence showed that the baby's parents had not moved him from the swing, bathed him or changed his diaper in nine to 14 days.

“He died of diaper rash. That’s right, diaper rash,” Coleman McAllister, an assistant Iowa attorney general, told jurors at Koehn’s trial.

>> Related story: Baby found dead in swing died of diaper rash, prosecutor says

Testimony from a Chickasaw County deputy who attended the boy’s autopsy indicated that maggots and their larvae were found on the boy’s body and in his clothing as the medical examiner removed the layers of urine-soaked blankets and clothing.

"As the diaper came off, you could see the skin had broken down," Chief Deputy Reed Palo testified in November, according to the Courier. "It just looked like it had been there a long time."

The boy’s diaper was full of feces and had attracted bugs, which laid the eggs that hatched into the maggots found during the autopsy. Prosecutors said Sterling developed diaper rash that became infected with E. coli bacteria.

Ultimately, he died of infection, malnutrition and dehydration. Testimony from first responders at Koehn’s trial indicated there were cans of formula in the kitchen and fresh diapers in the hot, smelly bedroom where Sterling’s cold, stiff body was found.

Medical examiner Dr. Dennis Klein testifies Thursday, Nov. 1, 2018, in the first-degree murder trial of Zachary Koehn, who was convicted Tuesday, Nov. 6 of murder and child endangerment causing death in Mount Pleasant, Iowa. Jurors took under an hour to convict Koehn, 29, of Alta Vista, in the August 2017 death of his 4-month-old son, Sterling Daniel Koehn, who was found dead in a baby swing in the family's home. The baby, who Klein testified had not had a diaper change in at least nine days, died of a combination of infection caused by diaper rash, malnutrition and dehydration. Found with maggots in his diaper and urine-soaked clothing, the boy weighed just a few pounds over his birth weight when he died. Credit: Jeff Reinitz/The Courier via AP Credit: Jeff Reinitz/The Courier via AP

A defense psychologist who testified on Harris' behalf said she suffered from severe depression, post-traumatic stress disorder and substance abuse, the Courier reported.

A prosecution psychiatrist testified, however, that he saw nothing in his own interviews with Harris that would have prevented her from caring for her son.

"Neither in what Ms. Harris told me was going on nor in the record do I find anything that indicates to me that she was so severely impaired that she could without knowing it watch her infant son starve to death," Dr. James Dennert testified Tuesday, the newspaper said. "That would require a pretty significant level of impairment that I just don't see and hasn't been described to me by Ms. Harris."

Dennert said depression would have had a wider impact on Harris' life and would not have been isolated to her interactions with Sterling, the Courier reported. Harris was able to care for her daughter, herself and the family's home, to the point where a friend of the couple's testified at Koehn's trial that he never knew the couple had an infant son or suspected anything was amiss when he visited.

Cheyanne Harris, left, and Zachary Koehn Credit: Chickasaw County Sheriff's Office/AP Credit: Chickasaw County Sheriff's Office/AP

Michael O’Hara, the clinical psychologist and University of Iowa professor testifying for the defense, said Harris’ PTSD stemmed from childhood sexual abuse. She also had a history of using methamphetamine, including after her son was born.

O'Hara testified that Harris was prescribed an antidepressant following the birth of her daughter, but she stopped taking the medication after a couple of weeks, the Courier said. He told the court the previous diagnosis made it more likely that Harris' depression returned after Sterling's birth.

Upon cross-examination, however, O'Hara conceded that Harris had told him she didn't want to change Sterling's diapers, that she was tired of hearing him cry and that her daughter would become upset any time she paid attention to the new baby, the newspaper reported.

“During your interview with the defendant, she admitted to you that she did not want anything to do with Sterling,” Assistant Iowa Attorney General Denise Timmins said.

“She said that,” O’Hara responded. “She was, I think, that disturbed but, yes, that was part of the interview, that she would be feeling that way about her son, (but on) another occasion, (she) said how much she loved him. That level of impairment in her functioning would be, I would call that quite disturbing.”

Zachary Koehn testifies in his own defense Friday, Nov. 2, 2018, in his first-degree murder trial at the Henry County Courthouse in Mount Pleasant, Iowa. Jurors took under an hour to convict Koehn, 29, of Alta Vista, on Tuesday, Nov. 6, 2018, of the August 2017 death of his 4-month-old son, Sterling Daniel Koehn, who was found dead in a baby swing in the family's home. The baby, who had not had a diaper change in at least nine days, died of a combination of infection caused by diaper rash, malnutrition and dehydration. Found with maggots in his diaper and urine-soaked clothing, the boy weighed just a few pounds over his birth weight when he died. His mother, Cheyanne Renae Harris, 21, still faces trial on murder and child endangerment charges. Credit: Jeff Reinitz/The Courier via AP Credit: Jeff Reinitz/The Courier via AP

Koehn, who worked as a truck driver, testified at his own trial that he trusted Harris to care for their son and their 2-year-old daughter, who was healthy at the time of her baby brother's death, the Courier reported. He told jurors he worked between 70 and 80 hours a week and, although he occasionally fed his infant son, he never changed his diapers because the smell made him queasy.

Harris' lawyers wanted Koehn to testify at her trial but, because of his pending appeal, he invoked his Fifth Amendment right against self-incrimination, the newspaper said.