On the morning after winning Minnesota's most watched homicide trial in years, Pete Orput sank into a chair exhausted, struggling with his emotions.

Two teenagers were dead, and the man who killed them was now going to prison for the rest of his life.

"This has just wiped me out. This is just so sad," Orput said Wednesday, acknowledging that the recent trial in Little Falls, Minn., kept him so preoccupied that he hardly slept.

"It was a tragedy for the kids. It was a tragedy for that homeowner. I'm assuaged that the jury found justice in it because it was a gratuitously awful murder and it didn't have to happen."

Orput, Washington County's chief prosecutor and a notable advocate for children, said there's no cause for celebration in Tuesday's first-degree murder conviction of Byron Smith, who shot and killed teenage cousins Nick Brady and Haile Kifer after they broke into his home on Thanksgiving Day 2012.

"These two kids should have been caught, should have been prosecuted, learned a lesson, paid a price and gotten back to their lives," said Orput, who has prosecuted more than 35 murder cases in his decades-long career. "Two kids who will never come back, dead, and an old guy who really didn't want to hurt anybody his whole life, snapped, killed two kids gratuitously, and now he's done, too."

Orput, the Washington County attorney since 2010, agreed to prosecute the case at the request of the Morrison County attorney after that small office became overwhelmed with felony cases, he said. To help, he enlisted his chief assistant, Brent Wartner, who in 2004 successfully prosecuted a high-profile home invasion in Long Prairie, Minn., that resulted in the killing of three family members. Throughout Smith's 2½-week trial, the two attorneys took turns questioning witnesses and addressing the jury.

But even 17 months after the killings, Orput said he's disheartened by how a senseless chain of events led to an armed confrontation and so much misery.

Crimes against children rile the former Marine, especially when he knows someone should have intervened and helped correct their behavior.

In his first term in Washington County, Orput has led a crusade for children, bringing increased attention to truancy, child abuse and other problems. The lure of drugs, including opiates and more powerful types of marijuana, has ruined many young lives, he said, and addiction to social media — and bullying that comes with it — adds even more challenges.

"They're wired to it, they stay up late at night, they text and Facebook, and the peer pressure's gotten, in my view, exponentially more difficult for kids," he said.

Wartner and Orput said that over the course of the Smith trial, it became wearing and emotional for everyone in the courtroom to hear disturbing audio recordings of the shootings "mostly because of how horrible the evidence was," Wartner said.

"Every time that audio was played, anybody who listens feels like they're walking with the teenagers who are going down those stairs. I feel like I've been scarred by that audio because I've listened to it so many times."

Orput, a gun enthusiast, said the case was never about the right to defend a home, but about a man obsessed with burglaries who set a trap for unarmed kids. He said he's worried many armed homeowners could wind up like Smith.

"You can kill somebody coming into your house if you believe they're going to commit a felony, but do you want to? Do you want to do that?" he said. "You're going to live the rest of your life with the regret that you killed somebody over property."

Dealing with victims' families, Orput said, can be difficult for prosecutors because of the expectations to win a conviction. But for him, the worst part comes at trial's end as he reflects on their emotional pain.

"When I get done," he said, "I feel like a big sliver of my spirit got cut out."

Kevin Giles • 651-925-5037