57-year-old Ginger Jefferson's trial is set to begin with jury selection on Monday. She is charged with first-degree murder.
Initially, police thought Jefferson was a material witness in the death of 32-year-old Kerry O'Clair-Jefferson last September.
O'Clair-Jefferson's body was found inside her Tama house by police, who were there to arrest her husband, Dustin Jefferson, on a warrant.
Evidence found inside O'Clair-Jefferson's home led police to conclude that Jefferson was responsible.
An autopsy shows O'Clair-Jefferson died of stab wounds to her neck.
Tama is a central Iowa city of around 2,900 that sits about 20 miles east of Marshalltown.