A Florida grand jury on Wednesday indicted Lois Riess on a charge of first-degree murder with a firearm and set a Monday court date to arraign her.
The first-degree murder charge, which carries a mandatory sentence of life in prison, replaces the second-degree murder charge filed last month.
Riess, 56, is accused of killing a woman who had a similar appearance to her in a Fort Myers Beach condo in April. She had previously been charged with second-degree murder. In Florida, only a grand jury can bring a charge of first-degree murder, said Samantha Syoen, a spokeswoman for the Florida State Attorney's Office.
Riess "committed a deliberate and premeditated murder warranting this charge," said Chief Assistant State Attorney Amira Fox.
Riess, of Blooming Prairie, Minn., also faces felony charges of grand theft, grand theft of a motor vehicle and criminal use of personal identification of a deceased individual in the Florida.
Authorities believe Riess killed Pamela Hutchinson sometime between April 4 and April 9 and took off with her car, cash and identification. Riess was the subject of a nationwide search after the killing. She was arrested in South Padre Island, Texas, on April 19 and extradited to Lee County, Florida, where she remains in the county jail.
Riess has entered a not guilty plea.
Lee County Undersheriff Carmine Marceno said "endless and tireless" work by authorities from multiple agencies led to Wednesday's indictment.
"We hope this indictment can help bring closure to the family of the victim," he said.
Riess is also a suspect in the shooting death of her husband, David Riess, in March. She has not yet been charged with the Minnesota killing, but charges are expected, a spokeswoman for the Dodge County Attorney's Office said Wednesday.
Riess has been charged in Dodge County for allegedly forging $11,000 in checks from her husband's business account.