WIESBADEN ARMY AIRFIELD, Germany — He felt “helpless.” The Iraqi man’s movement — his arm “flapping around” and the gurgling sounds he was making — were disturbing, Capt. Roger Maynulet told the jury.

“He was in a state I didn’t think was dignified. I had to put him out of his misery,” Maynulet said.

Maynulet, 30, a 1st Armored Division tank company commander, testified in his own defense Wednesday at his court-martial at Wiesbaden Army Airfield.

Maynulet is charged with assault with intent to commit murder in the death of Karim Hassan Abed Ali al-Haleji on May 21, 2004. If convicted, he will face a maximum penalty of 20 years in prison.

Maynulet on Wednesday admitted to twice shooting the wounded man, the driver of a car Maynulet’s unit had been ordered to capture or destroy because of a supposed “high-value target” inside.

“I fired a round at the Iraqi’s head. I missed the first round. I fired low. I readjusted and I compensated for that,” Maynulet said.

Capt. Will Helixon, one of Maynulet’s defense lawyers, asked his client if he thought he was authorized to do that.

Maynulet said yes.

“It was the right thing to do,” he said. “It was the honorable thing to do.”

Maynulet, a Chicago doctor’s son who attended Catholic schools and joined ROTC in college, was composed throughout his hour-long testimony.

His answers were matter-of-fact but not abrupt, his tone pleasantly neutral.

His control faltered just once: After he testified that he’d had to put the man out of his misery, Maynulet rubbed his face.

Maynulet testified that after the car they’d been briefly chasing crashed and he’d seen the extent of the driver’s injuries, he felt “helpless.”

“It was — oh — it was disturbing,” Maynulet said. “I felt — ah — pretty helpless. It’s hard to describe, you’re so used to be able to affect events. I was so used to fixing Iraqis.”

Mercy killing is forbidden, prosecutors say, by the rules of engagement, the laws of war and the Uniform Code of Military Justice.

But experts say that although mercy killing is not a legal defense, such a claim can sometimes persuade jurors to acquit or can lower a convicted defendant’s sentence.

The defense began its case Tuesday. Helixon read a batch of letters to the court-martial panel written by people Maynulet had known throughout his life, starting with his elementary school principal, a Benedictine nun.

“It’s my opinion Roger is a very kind, non-violent and peaceful person,” the nun wrote.

There were also letters from fellow officers, former commanders and trainers, and two Iraqi men Maynulet had worked with while deployed. All described him in glowing terms, mentioning his intelligence, compassion, good judgment, leadership, and his cool in the most trying combat circumstances. Maynulet’s parents and his wife, a former Black Hawk pilot who recently resigned her commission, sat behind him in the courtroom.

The defense started its case with testimony about Maynulet’s character for two reasons, said Capt. Clinton Campion, Maynulet’s other defense lawyer.

The first was timing: Some witnesses, including those expected to come from Iraq, weren’t available yet. The second reason underscores a major difference between civilian and military trials.

Civilian juries typically don’t hear about a defendant’s character until the sentencing phase, after a jury or judge has already decided the facts of the case and rendered a guilty verdict. But in courts-martial, panels and judges are allowed to give what’s called “character evidence” a great deal of weight in deciding the verdict.

“You’ve heard testimony about the character traits, and [the panel] can find reasonable doubt on that alone,” Campion said. “The UCMJ is a unique animal.”

The defense planned a total of 14 character witnesses. On Wednesday, an Iraqi official from Baghdad took the stand to say Maynulet is “a good soldier, a good officer ... very compassionate.”

Wednesday’s witnesses also included an Army neurosurgeon and a former neurosurgeon from North Carolina who’s now a lawyer, testifying for the defense.

Both agreed that it was possible the Iraqi man was already brain dead when Maynulet shot him. Both based their testimony on video from an unmanned drone that was monitoring Maynulet’s unit’s mission and which brought the shooting to authorities’ attention.

But the prosecutor’s neurosurgeon told the court that the wounded Iraqi was alive.