Smith was charged with aggravated murder, and prosecutors initially said they intended to seek the death penalty.
But last year, Washington County prosecutors said they were taking the death penalty off the table at the request of the victim's family "in an effort to avoid the delays associated with litigating a capital homicide case."
Going into his 10-day trial, Smith still faced a charge of first-degree felony aggravated murder which is punishable by a maximum sentence of life in prison without parole.
The charge was based on a number of aggravating factors, including that Christensen's slaying was committed during an episode where another person was killed.
Just before Smith killed Christensen on Dec. 11, 2010, his friend, Paul Clifford Ashton, 36, shot and killed 27-year-old Brandie Sue Dawn Jerden and shot and wounded James Fiske. Ashton, 36, was sentenced in 2013 to life without the possibility of parole for killing Jerden.
Jurors in Smith's trial found there were three aggravating factors that supported the charge: that Christensen's slaying was committed during an episode where another person was killed, that it was committed in connection with a kidnapping and that it was committed in an especially heinous, atrocious, cruel or exceptionally depraved manner.
The jury, however, reduced the aggravated murder count to a lesser count of murder, finding that "special mitigation" applied.
Defense attorney Gary Pendleton and co-counsel Mary Corporon had argued that Ashton, whom Pendleton has previously referred to as "the devil," intimidated Smith into committing the homicide, according to the Spectrum newspaper of St. George.
"Brandon Smith killed Jerrica Christensen, but he didn't do it because he wanted to silence her," Pendleton said, according to The Spectrum. "He killed her because he was afraid. He was afraid to say 'no' to somebody [Ashton] who he had just seen shoot two people."