Zachary Koehn: Sterling’s Death, Trial, Sentence, and Appeal

Zachary Koehn is an Iowa father who was convicted of first-degree murder in the 2017 death of his four-month-old son, Sterling Koehn, and sentenced to life in prison without the possibility of parole. Sterling was found dead in a powered baby swing in the family’s Alta Vista apartment after being left in the same diaper for roughly ten to fourteen days. He died of malnutrition, dehydration, and an E. coli infection caused by prolonged contact with his own waste.¹

How Sterling Koehn Died

On August 30, 2017, around 1:00 p.m., Chickasaw County deputies responded to an apartment on Hilltop Avenue after Koehn called 911. Prosecutors later said Koehn told the dispatcher the infant had died of sudden infant death syndrome.² Deputies found Sterling in a swing in a bedroom separate from where the parents and their older child slept. His diaper was filled with feces and infested with maggots, and blood was coming from his mouth.³

The state medical examiner ruled the death a homicide caused by a failure to provide critical care. Skin eroded by prolonged contact with feces and urine allowed E. coli into Sterling’s bloodstream. At nearly four months old, he weighed less than seven pounds, barely more than his birth weight and far below the fifth percentile for his age.⁴

Forensic entomologist Dr. Timothy Huntington examined scuttle flies on Sterling’s body and concluded the initial infestation began around August 20 or 21. That put Sterling in the same diaper and clothing for roughly ten to fourteen days before he was found. The hot room drew flies that laid eggs while the baby was still alive.⁵

The Household

Koehn worked as a truck driver, earning about $45,000 a year with health insurance. Prosecutors used the figure to counter any suggestion that poverty explained the neglect.² He and Sterling’s mother, Cheyanne Harris, shared the small apartment with Sterling and a nearly two-year-old daughter. The older child continued to be fed and cared for while Sterling was neglected.⁶

Methamphetamine use ran through the case. At arrest, Koehn told investigators he had last used meth two months earlier; Harris said she had used two to three weeks earlier. A friend, Jordan Clark, testified that he used meth with the couple and sold Koehn twenty to forty dollars’ worth a week. Clark also said that although he visited the apartment and knew about the older daughter, he had no idea Koehn had a baby son.⁷ At trial, Koehn also admitted he had questioned whether he was Sterling’s biological father.⁵

The Trial

Koehn was charged with first-degree murder and child endangerment resulting in death. Under Iowa Code § 707.2, a person commits first-degree murder by killing a child while committing child endangerment under circumstances manifesting extreme indifference to human life.⁸

Prosecutors argued Koehn intentionally withheld food, water, and care, telling the jury he “let Sterling rot in that room.”¹ The apartment was small, and the parents’ bedroom shared a wall with the room where Sterling sat in his swing. The smell alone, prosecutors argued, made it impossible for Koehn not to know.

Two evidentiary pieces cut hardest against him. Koehn’s employer produced truck weigh-in logs showing that in the five days before Sterling’s death, he had worked fewer than twenty-five hours, contradicting his claim that he worked seventy to eighty hours a week. And Dr. Dennis Klein, the chief medical examiner, testified that Sterling was too far gone by the day before his death to have interacted with Koehn the way Koehn described.⁵

Koehn’s public defenders, Steven Drahozal and Les Blair, called the death “a tragedy, not a crime.” Koehn took the stand and blamed Harris, saying they had an agreement that she would serve as the primary caregiver, that he assumed Sterling had died of SIDS, and that he had “put his trust in the wrong person.” He also told the jury he had a sensitive nose and stomach that kept him from changing diapers. On cross-examination, he acknowledged he took “better care of his dog” than he did of his son.¹ The defense asked the jury to consider involuntary manslaughter instead, arguing prosecutors had not proven malice.

Sentence

On November 6, 2018, the jury found Koehn guilty on both counts. The child endangerment conviction merged into the murder conviction under Iowa’s one-homicide rule, and Judge Stochl imposed the mandatory sentence for first-degree murder: life in prison without the possibility of parole. Koehn declined to speak at sentencing. Assistant Iowa Attorney General Denise Timmins noted the absence of anyone to speak for Sterling: “This is a mandatory sentence. There’s not much more that needs to be said. There are no victim impact statements or anyone else to speak on behalf of the child.”⁹

The Appeal

Koehn appealed to the Iowa Court of Appeals, raising four issues: that the evidence was insufficient, that the jury received an improper instruction letting it infer malice from child endangerment, that the murder conviction should have merged into the child-endangerment conviction rather than the other way around, and that the trial court wrongly admitted certain photographs.¹⁰

On November 4, 2020, the court affirmed the convictions in full. On sufficiency, it held that the small apartment, the shared wall, and employer records placing Koehn at home during much of the neglect period let the jury reasonably conclude he knew Sterling’s condition and chose to withhold care. The jury-instruction and merger arguments were treated as not preserved because trial counsel had not objected. The court also found no abuse of discretion in admitting the photographs, calling them relevant to Koehn’s claim that he was unaware of his son’s condition. Any ineffective-assistance claim was preserved for possible postconviction proceedings.⁵

Cheyanne Harris

Sterling’s mother was tried separately. On February 6, 2019, a jury convicted Harris of first-degree murder and child endangerment resulting in death, and she received the same mandatory sentence of life without parole. Her defense argued that postpartum depression and self-medication, not deliberate conduct, caused the death. Harris told an Iowa Division of Criminal Investigation agent, “I should have checked on him more.”²

Harris also appealed. On January 21, 2021, the Iowa Court of Appeals rejected her arguments, noting her attorney had agreed at trial not to seek a diminished-responsibility instruction and that under Iowa law such a defense is available only for specific-intent crimes, while the charges she faced were general-intent offenses.¹¹ Both parents are serving life sentences without the possibility of parole in Iowa’s correctional system.

1
Des Moines Register. Iowa Father Guilty of Murder in Death of Baby
2
Des Moines Register. Cheyanne Harris Iowa Mother Murder Trial
3
Oxygen. Cheyenne Harris Gets Life for Death of Son Sterling Koehn
4
News3LV. Criminal Complaint: Iowa Baby Found Dead Left to Rot in Swing for a Week
5
FindLaw. State v. Koehn, No. 18-2216
6
WISN. Mother Sentenced in Case of Maggot-Infested Infant Found Dead in Swing
7
UPI. Friend: Iowa Dad Kept Baby Secret Before Diaper Rash Death
8
Iowa Legislature. Iowa Code Chapter 707
9
Waterloo-Cedar Falls Courier. Zachary Koehn Sentenced in Infant Son’s Death
10
Iowa Courts. State v. Koehn, Case No. 18-2216
11
Des Moines Register. Cheyanne Harris Loses Appeal in Death of Infant Son Sterling Koehn