Murder, or accidental shooting?

On the day she died, Rebecca Tatum confided in her only sister that she had finally had enough. She would pack her things that evening, take her two young children and leave her boyfriend of almost seven years for good.

"She told me she was coming back to my place afterward," Roxann Kintner, Tatum's sister, told a jury in Yakima on Thursday.

But Tatum never did come back.

Kintner testified that the next time she saw her sister, she had been shot dead. She was the third witness to testify in the trial of Michael R. Spencer, who is charged with first-degree murder in Tatum's death.

Spencer insists the shooting, which occurred on Nov. 5, 2006, in their Lewis Road home in Naches, was an accident. He told sheriff's deputies he was examining his new 9 mm semi-automatic pistol and fired it, not realizing it was loaded. Tatum was 23 and five weeks pregnant when she died.

In opening statements earlier Thursday, Assistant Attorney General Justin Erickson argued that Tatum's death could not have been an accident.

The case is being handled by the state Attorney General's office because a potential conflict of interest arose within the county prosecutor's office last year. Yakima County prosecutors initially charged Spencer with second-degree murder, but the case was turned over to the state when one of the civil deputies was named a possible witness.

Prosecutors now allege that Spencer, now 26, intentionally killed Tatum in response to her attempt to leave him. They cited as evidence the existence of multiple gunshot wounds and also said Spencer himself was crying out on the night of Tatum's death that he was guilty.

"This was a relationship dominated by the defendant's jealousy and paranoia," Erickson told the jury, adding, "He tried to have total control over her life, but when she tried to leave he would not and could not relinquish that control."

However, the defendant is now pleading not guilty. John Crowley, a criminal defense attorney for Spencer, said the prosecutors only presented half of the story.

"He was hysterical and crying, according to the police," Crowley told the jury. "He couldn't carry on a conversation. If you killed someone accidentally that you cared for, you would have not been able to think straight either."

Crowley argued that results from the first two autopsies -- which concluded there were at least two gunshots fired into Tatum's body -- were inaccurate because investigators were influenced by preconceptions.

An investigation begun in March of this year by Kay Sweeney, a private expert who previously worked for the Washington State Patrol laboratory, was concluded in June.

After more than 50 hours of investigation, Sweeney determined that the seven gunshot wounds in Tatum's body all line up with a trajectory rod. Crowley said Sweeney concluded Tatum had been shot only once and that the various wounds were caused by a ricochet effect.

He said Spencer was handling his new pistol with his left hand, even though he is right-handed. The magazine was out of the gun, so Spencer didn't think the gun was loaded. But when he was checking to make sure, the gun discharged and struck Tatum as she sat in a nearby chair.

Crowley said that when the couple realized what had happened, they tried to walk together to the car to drive to the hospital. But Tatum collapsed, so Spencer began trying to drag her to the car. He said Spencer gave up and ran to a neighbor's house, crying hysterically for help.

Tanya Lucas, 32, who also testified, said she called 9-1-1 when Spencer approached her window, frantic, around 5 to 10 minutes after she heard a single gunshot.

But other witnesses remained convinced that Tatum was shot more than once.

Kintner told the court that Spencer was characteristically aggressive, and that this behavior escalated in the weeks leading up to the shooting. She said he would call every 45 minutes whenever she was spending time with Tatum to ask exactly what they were doing and when Tatum was going to be back home.

Tatum's mother, Diana Tatum, also testified. She said she always thought Spencer was excessively controlling, and that he yelled at Tatum a week before her death about the child she was carrying. Spencer believed it wasn't his.

Diana recalled in tears that she saw her daughter the morning of her death and urged her to end things with Spencer. But she said Tatum was afraid of what he would do.

Tatum died shortly after arriving at Yakima Regional Medical and Cardiac Center.

After the shooting, Spencer's parents received custody of the couple's children -- Payton, now 6, and Summer, who is 3 -- causing bitterness between the two families.

Tatum's family and friends were further infuriated when Spencer posted bail twice, once when his bail was reduced from $1 million to $250,000, and a second time after he returned to jail, the bail reverted to $1 million, because he violated the conditions of his release.

Crowley said Spencer will take the stand on his own behalf.

EDITOR'S NOTE: This story has been updated to correct erroneous information that appeared in the originally published version. Rebecca Tatum died on Nov. 5, 2006.