The Standard-Examiner reports 48-year-old Mark Anthony Ott entered the plea Wednesday following a long journey for the case that included a 2004 trial and a stop at the Utah Supreme Court.
Judge Michael Allphin sentenced Ott to 12 years to life in prison on charges including murder, theft and burglary.
Lacey Paige Lawrence died Sept. 1, 2002, in a fire prosecutors say Ott started at the house of his estranged wife, Donna Ott.
Lacey's father was dating Donna Ott at the time and was staying at the house with his daughter. Authorities say Mark Ott also stabbed Lacey's father and Donna Ott's teenage daughter during the break-in.
Information from: Standard-Examiner