The court at Katterbach Kaserne, part of the United States Army Garrison Ansbach, July 24, 2017, where the trial of the U.S. vs Brian Johnston is taking place.

The court at Katterbach Kaserne, part of the United States Army Garrison Ansbach, July 24, 2017, where the trial of the U.S. vs Brian Johnston is taking place. (Martin Egnash/Stars and Stripes)

ANSBACH, Germany — Army investigators who determined that a staff sergeant murdered his child failed to look into the 2-month-old’s pre-existing medical conditions, defense lawyers and the soldier’s wife said Monday.

Staff Sgt. Brian P. Johnston, 37, has been charged with murder in connection with the 2015 death of his son, Lukas.

The defense began presenting its case Monday on Day 7 of the court-martial, which could continue through the end of the week.

Prosecutors accuse Johnston of causing abusive head trauma, commonly known as shaken baby syndrome.

Lukas, who was born with Down syndrome and a hole in his heart, was diagnosed as suffering from “failure to thrive” after losing weight in his second month, defense attorney Aaron Meyer said.

Lauren Johnston, Lukas’s mother, told Meyer while testifying that she grew suspicious during questioning by investigators in 2015.

“Did you look into any of the medical conditions, or are you just trying to pin this on my husband?” Lauren Johnston said she recalled asking Army investigators.

Meyer said later that a German emergency room doctor who examined the boy treated Lukas without knowing about his prior conditions, which led to the false conclusion that the baby was abused.

“You didn’t know that he was losing weight, you didn’t know his heart was enlarged and you didn’t know he was losing blood flow to his left atrium, before treating him,” Meyer said.

The defense argued that Lukas sustained fatal injuries after rolling off an ottoman when he was briefly left unattended.

Prosecution medical experts testified earlier that the boy’s injuries were consistent with abuse.

“I couldn’t see any other cause of this,” said Thomas Voelkl, the head doctor of the emergency room where Lukas was taken. “There are other ways an infant can get these symptoms, but we’ve ruled them out.”

Voelkl was the first doctor to determine that the boy’s condition could have been the result of shaken baby syndrome.

Forensic pathologist Dori Franco, who examined Lukas’ body after death, found multiple contusions on different areas of the head, severe brain hemorrhaging and extensive retinal hemorrhaging.

“The cause of death, in my opinion, was head trauma,” she said.

Much of the defense’s case relies on Lukas’ well-being before his death. Meyer said that the baby’s diagnosis of “failure to thrive” and the pre-existing heart defect turned a minor fall into a fatal one.

That view, however, was disputed by Annette Lechler, a German doctor who helped deliver Lukas. She said Friday that he was healthy at birth and had been cleared to leave the hospital.

The defense said Lechler was hasty in her designation of Lucas as healthy, as he suffered myriad conditions days after his birth that resembled the symptoms he exhibited at death, such as a swollen face, discoloration and small bruises. Twitter: @Marty_Stripes

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