Officials say it took less than an hour for an Iowa jury to find a 28-year-old Iowa father guilty of murder after his 4-month-old son was found dead in a motorized swing last year, PEOPLE confirms.

Zachary Koehn was convicted of first-degree murder and child endangerment causing death, according to a spokesperson from the Office of the Attorney General for Iowa.

In Iowa, first-degree murder carries a mandatory sentence of life without parole.

On Aug. 30, 2017, authorities arrived to the home of Koehn and 21-year-old Cheyanne Harris and discovered the lifeless body of their son, Sterling Koehn, in the swing, according to a criminal complaint obtained by PEOPLE.

Both parents pleaded not guilty to first-degree murder charges in Sterling’s death.

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According to autopsy results, medical examiners found “maggots in various stages of development” in the boy’s “clothing and on his skin.”

During the trial, prosecutor Coleman McAllister, an assistant Iowa attorney general, told jurors that Sterling had worn the same diaper for nine to 14 days when medics were called to the family’s Alta Vista, Iowa, apartment, reports the Waterloo-Cedar Falls Courier.

The diaper’s contents irritated the baby’s skin, causing it to rupture, after which E. coli bacteria set in, McAllister said.

“He died of diaper rash. That’s right: diaper rash,” McAllister said during opening statements, according to the Associated Press.

Another prosecutor reportedly put it more bluntly: “He [Koehn] let Sterling rot in that room. He left him there to die.”

Authorities believe Sterling, who weighed less than 5 lbs. at death, was left in the baby swing for over a week and that he was not bathed or changed that entire time, according to the criminal complaint.

“The facts of this case go far beyond neglect and show circumstances manifesting an extreme indifference to human life,” Chickasaw County Sheriff’s Deputy Reed Palo wrote in the complaint.

Palo told jurors he found maggots and larva when the medical examiner began to remove the layers of urine-soaked blankets and clothing from the child, the Courier reports. The medical examiner determined Sterling died from failure to provide critical care, according to the Des Moines Register.

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Koehn’s defense attorney, Les Blair III, told jurors that Sterling was not the victim of a crime but rather a tragedy, according to the Courier. (Reached by PEOPLE, Les Blair III did not have any comment regarding the verdict.)

“Nothing anybody says throughout this trial will soften that,” he said.

Koehn is scheduled to be sentenced on Dec. 4 in Chickasaw County.

Harris is being tried separately and is expected to go to trial at a later date.