Minnesota Man Accused of Murdering Teens Who Entered His Home Retiree Byron Smith allegedly told police, "I wanted him dead."

April 22, 2014 -- The trial against a 65-year-old man accused of murdering two teens who entered his home is underway in Minnesota, stirring debate about how far people can go in defending their homes.

Byron Smith, a retired security engineer for the U.S. Department of State, is charged with first-degree premeditated murder in the slayings of cousins Nick Brady, 17, and Haile Kifer, 16, on Thanksgiving Day 2012. The killings rocked the small city of Little Falls.

Prosecutors say Smith was sitting in his basement when he heard a window breaking upstairs. When Brady started walking down the basement stairs, Smith shot him twice.

Then, according to court documents, Smith shot Brady a third time in the face, allegedly telling investigators, “I want him dead.”

Minutes later, Kifer walked down the same steps, reportedly calling Brady’s name. Smith shot her multiple times, too – telling investigators the last time he fired was “a good clean finishing shot.”

Steve Meshbesher, Smith’s attorney, said the case focuses on home security, that Smith had been worried after several break-ins.

“This was about anxiety and fear, and what somebody does in their own home,” Meshbesher said.

But prosecutors say Smith planned the killings – lying in wait for the two teens in his basement with a book, two guns, energy bars and a bottle of water. The teens weren’t armed.

Under Minnesota law, a person may use deadly force to prevent a felony from taking place in one's home. ABC News Legal Affairs Anchor Dan Abrams said the home-defense angle has limitations.

“The problem is that Byron Smith fired multiple shots,” Abrams said. “You don’t have the right to execute an intruder. If he had fired one shot at each of these intruders, he’d have a much stronger defense.”

The Associated Press contributed to this report.