Prosecutors called their star witness Friday in the murder trial of a woman who claims she killed an Iowa neighbor in self-defense: a former close friend who initially believed her account but came forward a decade later to provide key evidence against her.

Farmer Mary Higgins provided critical testimony to back up the prosecution's claim that Tracey Richter killed 20-year-old Dustin Wehde in a plot to frame her ex-husband and then falsely claimed she was the victim of a home invasion.

Richter has insisted the shooting at her home in Early, a small town in northwest Iowa, was in self-defense after Wehde and another man broke into her home.

Higgins described herself as a reluctant witness who once enjoyed Richter's company but later saw her as a dishonest woman who treated her children poorly and could explode in anger.

She said she and Richter became friends after Richter and her second husband moved to Early in 1998. They often spoke on the phone, had coffee together and she drove Richter's son home from school.

Richter flew to Australia for a planned family vacation days after Wehde was shot in December 2001. Higgins said they got together in January or February after she returned.

"I wanted to let her know that I stand by her," Higgins recalled.

But she said Richter showed no emotion and acted "like she was telling me her grocery list" when she recounted her version of events: that two men broke into her home and one choked her with pantyhose before she broke free, unlocked her gunsafe _ without her glasses in the dark _ grabbed two guns and shot Wehde while the other man fled.

Police never found a second intruder. Defense attorneys have suggested the second man was an ice cream delivery driver who was having an affair with Wehde's mother. The man, Iraq war veteran Jeremy Collins, testified Friday afternoon he had nothing to do with any home invasion and did not know Wehde well. Richter cried during his testimony and left the courtroom in tears.

Higgins said that while Richter was retelling her story, her 11-year-old son walked in and banged his head on the table.

"He said, `Why did you go back up there?'" Higgins recalled. "'You didn't have to shoot him. You didn't have to kill him.'" Richter screamed her son's name, and he left.

Higgins said Richter told her police found a pink spiral notebook in Wehde's car and "it would prove that John Pitman did this." But two years later, in 2004, Higgins said Richter pointed her finger and "told me that I needed to forget about the pink notebook, and it frightened me. Tracey could explode and then be calm."

Law enforcement officials have testified they kept the notebook a secret until this year because anyone who knew about it would have knowledge of the crime. Prosecutors say Richter, now 45, forced Wehde to write the notebook claiming Pitman, her ex-husband, hired Wehde to kill her and their son. They say she killed Wehde to keep him quiet and then planted the notebook in his car.

Pitman, a Virginia plastic surgeon, testified earlier Friday that he had nothing to do with the notebook. Richter and Pitman were fighting at the time over custody of their son, Bert Pitman.

Higgins said she didn't tell a detective who interviewed her in April 2002 about the notebook because she assumed investigators knew about it and they did not ask her. She said she was contacted in March 2011 after investigators re-examined the case and her husband had become church friends with the new Sac County prosecutor, Ben Smith.

Smith met with her at their home, and she told him, "I didn't want any part of this." But when he asked if she knew about details, she responded, "Do you mean that stupid notebook?"

"The blood drained from his face," she testified. "I'd never seen anything like that before. He just went on the ground and sat on the floor and leaned against the kitchen cupboards."

Division of Criminal Investigation agents then interviewed her, and Higgins said she told them about the notebook but not share the full details because she was afraid for herself and Richter.

"She was my friend and I didn't know where it was going," she said. "I didn't know what the notebook meant. I knew it wasn't good."

She said she went into more detail in a second interview with investigators. She said she asked Richter why a 20-year-old man would have a pink notebook and Richter responded that Wehde must have gotten it from one of his sisters. Higgins also recalled how, months before the shooting, Richter told her about buying Bert a pink notebook for school, and Higgins said her sons would never use one like that.

Her statements and other evidence were used to draft a complaint charging Richter with murder and leading to her July arrest in Omaha, where she was living. Higgins occasionally glanced across the courtroom at Richter, who looked away during her testimony.

Prosecutor Douglas Hammerand gave jurors photocopies of the journal's five pages written in Wehde's sloppy handwriting, and they followed along as he read aloud. The journal said Wehde wanted to make a record of a "mysterious fellow who asked me to work for him (John Pitman)."

Pitman "wants me to get/force" Richter to kill Bert and then commit suicide, or "make it appear as though T.R. had committed the murder of her son & then committed suicide," it said.

Pitman testified the journal described him accurately: a doctor from Virginia who wanted to follow in the footsteps of his father, also a surgeon, and take over his practice one day. The diary describes him as a white male in his 40s who was in the Army.

It named Pitman's divorce attorney, Stephen Komie. Only Richter and his family knew that much detail about his personal life, Pitman said, although he acknowledged on cross-examination that he had conflict with Richter's second husband, who could have gotten personal information about him from her.

The doctor said that he never met Wehde, did not hire him and did not want his son dead.

"Did your ex-wife Tracey Richter despise you?" Hammerand asked.

"I think so," Pitman responded with a laugh.