FORT DODGE, Iowa — The trial of John David Green, accused of killing a longtime friend and hiding the body in a basement where it lay undiscovered for three-plus years, ended in a mistrial Tuesday.

A defense attorney had objected to a statement by Sac City, Iowa, Police Chief John Thomsen. A new trial is expected but not yet scheduled.

Green, 55, is charged with first-degree murder in the 2009 death of Mark Koster in Sac City. The defense team says Green killed Koster in self defense.

Both sides made their opening arguments Tuesday morning at the Webster County Courthouse in Fort Dodge. Then prosecutors began calling witnesses. Thomsen was the second, and last, to testify.

Sac County Attorney Ben Smith asked Thomsen about themes investigators used while questioning Green. It was during an interview in Florida in March that Green told investigators he killed Koster with a baseball bat.

“We try to minimize the crime. We make the victim more to blame,” Thomsen told the jury. “Bad people, when they do something wrong, they don’t like to admit it, so we make it a little easier.”

Charles Kenville, one of two public defenders representing Green, objected. While the jury was away, Kenville argued that a mis­trial should be declared. Among the reasons was that his client would testify in his own defense, his credibility would be a major factor and an investigator had just described him as “bad people.”

Assistant Attorney General Doug Hammerand agreed that Thomsen shouldn’t have phrased his response as he did, but said the chief was talking generally, not specifically about Green.

District Court Judge Gary McMinimee, his voice halting, said he could count the number of mistrials he has presided over on one hand.

“This is the first these jurors have heard on this subject and is therefore most likely to be remembered,” the judge said.

“I asked a poor question, and the defendant is entitled to the presumption of innocence,” Smith told The World-Herald in a telephone interview Tuesday evening. “It wasn’t the (chief’s) fault.”

According to authorities and court documents, Green told investigators that he killed Koster in June 2009 after Koster attacked him with a baseball bat, then hid the body in the basement of Koster’s Sac City home.

Green was a house guest of Koster’s in the months leading up to the slaying. The two had known each other for about 30 years.

Green told investigators that during the struggle, he took the bat from Koster, 58, and hit him in the head. With Koster on the floor, Green got on top of him and used the bat to choke Koster and crush his throat. Green was on top of Koster for about 2 minutes, according to court documents.

Green stayed at the house for two or three days after the slaying, then traveled to his father’s home in Mississippi, leaving a note to make it appear that Koster had left Sac City to return later. Green cleaned up the house before leaving, according to court documents.

Koster was later reported missing. Police searched the home but found no signs of foul play. He was declared legally dead in 2011. The new homeowner was remodeling when he discovered Koster’s remains in 2012.

During opening arguments Tuesday, Smith said that after killing Koster, Green dragged him to “the darkest, deepest corner” of Koster’s basement, wrapped the body in bedding and concealed it with several bags of kitty litter and other items, including a 200- to 300-pound water heater.

Green made several contradictory statements to investigators, Smith said, including that he had never been to Iowa. But he changed his story when investigators showed him “unimpeachable” evidence that he had been there.

“This isn’t a case of self-defense,” Smith told the jury. “It’s just not.”

But Kenville said it was. He said Koster was mentally ill, having been diagnosed with paranoid schizophrenia in 1990. He had been behaving irrationally in the days leading up to the incident in which he attacked Green, Kenville said.

“He was sort of angry about everything,” Kenville said. “He was not in a good place mentally.”

Kenville acknowledged his client should not have hid the body and fled.

“People can make mistakes after the fact. That does not mean they are guilty of murder,” he said.

Koster’s brother, Daniel Koster, told jurors that his brother was one of 11 children. He had graduated from high school in St. Ansgar, Iowa, and later served in the U.S. Marine Corps, following in the footsteps of an older brother.

“He was a pretty friendly guy. He liked to fish. He liked to play cards,” Daniel Koster said.

Sac City is about 115 miles northeast of Omaha.

Contact the writer: 402-444-1310, andrew.nelson@owh.com

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