Is Heather L. Horst a "coldhearted" manipulator who plotted her husband's murder? Or is she simply an innocent widow who had no inkling her friend planned to shoot her husband as he slept in their home?

Those are the questions jurors will face in coming days when they deliberate Horst's fate in a murder trial that began this week in Ramsey County District Court.

Prosecutors and Horst's attorney presented wildly different pictures of the 25-year-old St. Paul woman Thursday during opening statements. Horst is charged with aiding and abetting first-degree murder, aiding and abetting second-degree murder, conspiracy to commit first-degree murder and conspiracy to commit second-degree murder in the death of Brandon J. Horst, 26, at the couple's home on the West Side.

Assistant Ramsey County Attorney Jada Lewis told jurors that Horst tricked her friend Aaron W. Allen, 26, into carrying out the "execution" shortly after midnight on Aug. 5.

"He was a son, a brother, a gifted and talented tech sergeant with the Minnesota National Guard," Lewis said of Brandon Horst.

But Heather Horst's attorney, Deborah Ellis, said Allen acted on his own, without help from Horst, carrying out a murder fantasy he had plotted before he befriended her.

Lewis told jurors that Brandon and Heather Horst were married in December 2010, but that by the summer of 2013, their marriage was crumbling because of financial strain and allegations of infidelity by Heather Horst. The couple fought "constantly." But instead of divorcing, Lewis said, Horst hatched a plan to murder her husband and inherit his $488,000 life insurance policy.

Horst preyed on Allen's history of physical, sexual and emotional abuse, Lewis said, telling him lies about abuse she allegedly suffered at the hands of her husband — abuse, she told Allen, that caused her to miscarry multiple times.

When Allen pleaded guilty in March for his role in the killing, prosecutors revealed that Horst was never pregnant. Allen pleaded guilty to second-degree intentional murder and agreed to a 40-year prison term. He's to be sentenced June 10.

Ellis warned jurors to be skeptical of Allen's story. She told them that Allen and his friends had discussed ways to commit murder, including shooting someone and dumping the body at an Iowa hog farm or slitting the victim's throat and soaking the body in lye.

"That was his time to kill," Ellis said of Brandon Horst's murder. "[Allen] and his friends had a fantasy that they talked about over and over again. Aaron Allen carried out that fantasy."

At his plea hearing, Allen testified that he and his friends had regularly discussed murder plots. Two of those friends initially agreed to help kill Brandon Horst but backed out.

Allen was engaged to Brandon Horst's stepsister in 2013 and befriended Heather Horst that summer.

Allen testified Thursday that Horst told him that her husband abused her and took away her cellphone and car keys. She said she couldn't divorce him because she'd lose her home and car and be disowned by her family. Allen said he sympathized with her because he saw his mother abused. He said he also was abused.

Allen also testified that he lost it when Horst told him on Aug. 4 that Brandon Horst punched her in the stomach, causing her to miscarry again.

"I saw blood," Allen said.

Horst allegedly then hatched a murder plot with Allen and his two friends and later dropped Allen off at the Horst home, Lewis said. Allen then waited in the basement, crept up the stairs and fired one shot into Brandon Horst's right eye, the bullet traveling through his left arm as he slept on it.

When Horst picked up Allen afterward, Lewis told jurors, her first words were: "How many rounds did you put in him?"

Chao Xiong • 612-270-4708

Twitter: @ChaoStrib