Smith, 66, was quickly sentenced to life in prison Tuesday. He was free on bail during the trial but was taken into custody in the courtroom.
Haile Kifer, 18, and her cousin, Nick Brady, 17, were shot on Thanksgiving Day in 2012 in the basement of Smith's home in Little Falls, a small city on the Mississippi River about 75 miles northwest of Minneapolis. While Smith's defenders say he had the right to protect his home, prosecutors said he set a trap for the teens by making his home look like it was empty.
Smith, who had parked his truck at a neighbor's property, waited in the basement. He was in a comfortable chair with a book and guns.
Jurors, who deliberated for only three hours before reaching their verdict, said it was not a close call.
“It seemed like he had done many things to either lure them into the house or into the basement itself,” Thomas Strandberg told the Minneapolis Star-Tribune. “Moving the truck was the very first big sign that he had planned something. And then moving the bodies and having the tarp handy had a lot to do with it.”
Smith declined to testify during his trial, and told the judge he had nothing to say before sentencing. His lawyer says he plans to appeal.
Relatives conceded in victim impact statements that the two teenagers were breaking the law when they were shot.
“Smith was robbed of things," Brady's grandmother, Bonnie Schaeffel, said. "Nick and Haile were robbed of their lives.”
Smith, retired as a State Department security expert, set up recording equipment in the basement. Jurors heard the shootings and Smith telling Brady "you're dead" and offering Kifer an apology as he shot her.
He did not call police immediately. Instead, he consulted a neighbor the next day about getting a lawyer.
Notable deaths of 2014 [PHOTOS]