He killed her, Joshua Stepp admitted. He slammed the face of his 10-month-old stepdaughter into a carpeted floor, roughed her up as he changed her diaper, stuffed wet toilet paper down her throat, and soon she was dead.

But Stepp, a 28-year-old former Army infantryman who saw combat in Iraq, insists that he is not guilty of first-degree murder. His post-traumatic stress disorder left him incapable of premeditating the killing of tiny Cheyenne Yarley in November 2009, he and his lawyers say.

Because of his severe PTSD, Stepp was not able to “form the specific intent to kill,” his attorney Thomas Manning said. He asked jurors last week to find Stepp guilty of the lesser charge of second-degree murder, which lacks the potential for the death penalty.

After a decade of combat overseas, growing numbers of veterans are relying on PTSD as a central element of their defenses in criminal cases. Stepp’s trial is being closely watched as one measure of just how far defense lawyers are able to push in arguing that the disorder influences veterans’ criminal behavior.


The number of such cases will rise as more veterans return from Afghanistan and Iraq with post-traumatic stress or other trauma from repeated combat tours; already, more than 170,000 veterans from Iraq and Afghanistan have been diagnosed with PTSD, according to the Department of Veterans Affairs.

Thousands of veterans accused of nonviolent crimes have had charges or sentences reduced in the last several years after citing their PTSD as a mitigating factor. Veterans with combat trauma are now often sent to counseling and treatment programs rather than to prison for low-level offenses.

“The idea isn’t to get the guy off; it’s to help the veterans get the treatment they need. They deserve our help,” said Shad Meshad, founder of the National Veterans Foundation and a Vietnam veteran who has counseled soldiers for 40 years.

The prosecutor in the Stepp case told jurors that his defense insults veterans because it “taints their suffering” and “perverts this disease.”


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On the night Stepp killed Cheyenne Yarley, he had downed rum, bourbon and beer, plus painkillers prescribed for his wife, an Army veteran and Cheyenne’s mother, his lawyers said.

He was angry about being called home from a bar by his wife to care for Cheyenne and Stepp’s 4-year-old daughter from a previous marriage, his lawyers said. His wife had to go to work.

In vague, halting testimony a prosecutor called “convenient,” Stepp said he couldn’t recall many details of that night. Cheyenne died of head trauma from multiple blows.


“I can only, like, remember really intense parts,” he testified.

He added later: “I don’t know, it just like happened, and then I’m there and I’m like, ‘What the hell?’”

Stepp’s PTSD and his drug and alcohol abuse left him incapable of plotting or intending Cheyenne’s murder, Manning said.

“People with untreated PTSD do not have the same checks and balances, or brakes, that the rest of us hopefully do,” Manning told jurors.


Stepp had seen fellow soldiers blown apart by roadside bombs in Iraq, his attorney said in court. In one instance, he had to put those pieces in the container available to him: a pizza box.

When Stepp came home from Iraq, he grew more and more damaged by deepening PTSD, his attorneys said. The night Cheyenne died, she wouldn’t stop crying and kept soiling her diapers, and Stepp lost control, Manning said.

“There is no pity being asked,” Manning told the jurors. All he asked was for them to find that Stepp’s PTSD left him incapable of deliberately killing his stepdaughter.

But prosecutor Boz Zellinger pointed out that Stepp repeatedly lied to his wife over the phone and to a police dispatcher while his stepdaughter was dying in the family’s apartment.


“What shows his competency more than his deceit?” Zellinger asked the jury. “He had a fixed purpose: to kill that child so no one would see what he had done to her.”

He added: “Every single piece of evidence shows the defendant was in control of his actions that night.”

Zellinger scoffed at Stepp’s PTSD claims, saying defense experts relied entirely on Stepp’s own, unreliable statements in concluding that he suffered from the disorder.

He raped Cheyenne intentionally, the prosecutor said. Blood was found on Stepp’s underwear, Zellinger said, and the girl’s injuries were so severe they could not possibly have been caused by vigorous wiping. “Every orifice that Cheyenne had was injured,” Zellinger said.


But Stepp denied sexually abusing Cheyenne; Manning said that the bruises around the infant’s anus and vagina occurred when Stepp wiped her roughly as he changed her diaper.

On Sept. 8, a jury of six men and six women found Stepp guilty of first-degree murder and sexually assaulting his stepdaughter.

Manning immediately began putting on witnesses in the penalty phase, where Stepp’s PTSD remained central to the lawyer’s attempt to save the veteran from the death penalty.

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Courts and prosecutors are far more willing now than during the Vietnam era to consider a veteran’s combat trauma in sentencing for nonviolent crimes, lawyers say. Veterans’ groups credit a growing awareness of PTSD, activism by advocates for the mentally ill and a nation sympathetic to the conditions under which soldiers must operate.

“There is definitely a recognition that the emotional and psychological scars of our veterans are real,” said Stephen Saltzburg, general counsel for the National Institute of Military Justice, which studies the military justice system.

A unanimous U.S. Supreme Court decision in 2009 helped pave the way for combat trauma — and military service itself — to mitigate sentences. In that case, the court reversed the death sentence for a Korean War veteran because his military service and combat-induced psychological damage weren’t presented at sentencing.

Noting that the U.S. has “a long tradition of according leniency to veterans in recognition of their service,” the court said “juries might find mitigating the intense stress and mental and emotional toll” of combat.


Today, more than 80 special veterans’ treatment courts have been established nationwide and hundreds more are planned, said Christopher Deutsch, a spokesman for the National Assn. of Drug Court Professionals.

Veterans’ courts do not provide “a get-out-of-jail-free card,” said Brockton D. Hunter, a Minneapolis lawyer and veteran who since 2002 has represented more than 100 veterans diagnosed with PTSD. Instead, the courts steer defendants toward treatment and probation, often working closely with Department of Veterans Affairs medical centers.

Although many prosecutors are sympathetic to combat veterans, some PTSD-related defense tactics are viewed with skepticism.

“Prosecutors are always wary of the ‘defense of the day,’ or trends that … may be overused because there is some perceived broader understanding or acceptance by courts and juries,” said Scott Burns, executive director of the National District Attorneys Assn.


The law, said Elizabeth Hillman, a law professor and president of the National Institute of Military Justice, “is uncertain and evolving.”

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On Tuesday, jury members told Judge Osmond Smith that, after deliberating for two days, they could not reach a unanimous verdict on a sentence. Following state law, the judge sentenced Stepp to life in prison without the possibility of parole.

david.zucchino@latimes.com