WILLMAR, MINN. – A Willmar teenager was sentenced Wednesday to life in prison for his role in his grandmother's murder, wrapping up what one family member called "the final chapter in a sad, sad story."

Robert Inocencio Warwick, 18, pleaded guilty in Kandiyohi County District Court to first-degree murder while committing a felony, the burglary of his grandmother's home. Another count that carries a tougher penalty — first-degree, premeditated murder — was dismissed.

District Judge David Mennis sentenced Warwick to life in prison with the possibility of parole after 30 years.

The sentence comes nearly a year after a friend of the teen stabbed and strangled Lila Warwick, 79, whom family and neighbors remember as a doting grandmother and devoted church volunteer.

Robert Warwick apologized Wednesday to his family members, several of whom wept in the courtroom.

"I hope one day everyone will forgive me," he said. "I want to say sorry to my grandma, who's watching over me every day of my life."

Cheri Ekbom, Lila Warwick's daughter and Robert Warwick's aunt, took the witness stand to face the third teen charged in her mother's murder and to give her third victim impact statement.

"But regrettably, today is different," she said. "Unlike the others, I do not look into the eyes of a stranger, but that of family. My nephew, Robbie Warwick."

There are still "unanswered questions," she said. "Really, just one: Why?" Ekbom asked, staring at her nephew, who wiped tears away with the sleeve of his orange sweatshirt.

In the year since Lila Warwick was left handcuffed and bleeding in the basement of her rambler on the east edge of Willmar, three teens have pleaded guilty in the crime.

Brok Junkermeier, 20, who strangled and repeatedly stabbed Lila Warwick, pleaded guilty in April to first-degree, premeditated murder and was sentenced to life in prison without the possibility of parole. Devon Jenkins, the 16-year-old who acted as the lookout, pleaded guilty in December to aiding and abetting second-degree murder.

Supreme Court uncertainty

Because Robert Warwick was 17 years old at the time of his grandmother's slaying, his sentence had he been convicted of first-degree, premeditated murder would have been uncertain, prosecutors said Wednesday.

In 2012, the U.S. Supreme Court ruled in Miller vs. Alabama — a case involving a 14-year-old boy — that sentencing juveniles to spend life in prison without considering factors like their youth, motive and potential for rehabilitation violated the Constitution's prohibition on cruel and unusual punishment.

"Because of that, there is some uncertainty about the penalty," said Matthew Frank, assistant attorney general, in explaining the plea deal.

Since the beginning, prosecutors have said that Robert Warwick hatched the plan to rob and murder his grandmother, giving Junkermeier information about her house and habits — including what time she awoke and where she hid a spare key.

During his trial, Junkermeier testified that he and Warwick had been planning the early-morning ambush robbery and attack for months.

But on Wednesday, Warwick said the pair had been planning a burglary — but not a murder — for only a month. During questioning by his attorney, Daniel Mohs, Warwick admitted that he knew Junkermeier would bring a large knife to his grandmother's house "to intimidate her."

Given that and other factors, Warwick said he knew it was "foreseeable" that the plot could leave his grandmother dead.

Soon after the murder, Warwick told investigators that because of his grandmother's frailty, Junkermeier could have killed her simply by pushing her over, Mohs said.

"And you were OK with that?" Mohs asked Warwick. "Yes," he answered.

Outside the courthouse, Mohs said that while evidence had emerged that might have led a jury to convict his client of premeditated murder, Warwick was going to testify that murder was never the plan. Instead, Mohs said, things went "haywire" when Lila Warwick fought back against Junkermeier.

"All I can tell you is that my client has never told me that there was a plan to murder his grandma," Mohs said.

But Ekbom criticized her nephew for not taking "full responsibility for all of his actions in the murder and betrayal of his grandma, my mom."

Junkermeier and Jenkins "had the courage to own up to their involvement," she said. "I would expect nothing less from my nephew — in fact, much more."

But instead, she said, Warwick copped only to the provisions outlined in the first-degree count to which he pleaded guilty. He repeatedly said that it was "foreseeable" that Junkermeier might kill his grandmother while burglarizing her home — a key word in the statute outlining the crime. That ignores the evidence and interviews that show he planned the murder, Ekbom said.

"This horrid, thought-out crime clearly started with Robbie," Ekbom said. "And with his complete admission of guilt, it ends with him."

Jenna Ross • 612-673-7168