ST PETERSBURG, Florida (AP) - A Minnesota woman who led authorities on a cross-country manhunt pleaded guilty on Tuesday (Dec 17) in a Florida courtroom to fatally shooting a woman who prosecutors said was targeted because the two looked alike.

Officials from the Lee County State Attorney's Office said Lois Riess, 57, singled out Pamela Hutchinson because they shared similar features, and because Riess wanted to assume Hutchinson's identity while on the lam.

She was sentenced to life in prison.

With a shock of white hair, Riess garnered national attention as the "fugitive grandma" before she was captured on April 19, 2018 in Texas.

Riess' saga began in March of that year, when her husband, 54-year-old David Riess, was found dead at the couple's Blooming Prairie, Minnesota, home.

Lois Riess forged cheques to steal US$11,000 (S$15,000) from her husband's account, travelled south to Florida and landed in Fort Myers, prosecutors said.

Investigators said surveillance footage showed the two women near Hutchinson's Fort Myers condo-hotel room on April 4 and April 5.

For the next two days, Riess was recorded on surveillance video - at times carrying garbage bags to the parking lot - but Hutchinson wasn't seen at all.

After killing Hutchinson, Riess made her way to Texas while using Hutchinson's credit cards and vehicle, police said.

On April 19, 2018, Riess was drinking cocktails at a South Padre Island, Texas, waterfront restaurant when she was arrested by two federal deputy marshals.

An employee recognised her from surveillance video broadcast on TV.

On Tuesday, Riess pleaded guilty to first-degree murder with a firearm, grand theft of a motor vehicle, grand theft, and criminal use of personal identification information of a deceased individual. Prosecutors withdrew the possibility of the death penalty on the murder charge as part of the plea deal.

Samantha Syoen, the spokeswoman for the State Attorney's Office, wrote in a news release that Hutchinson's family was supportive of the plea agreement because they wanted Riess to be incarcerated for the rest of her days.

"This defendant will never get out of prison," said State Attorney Amira Fox.

"This life sentence also alleviates any appellate issues that could arise and guarantees she will never be free again. It also allows the family of the victim to not have to go through the details of this crime at a trial."

Riess waived extradition on Tuesday to face charges in Minnesota in connection with her husband's slaying. Messages left with authorities in Minnesota were not immediately returned on Tuesday.

Her son, Braden Riess, said in 2018 that she was a "good lady" but had her "own demons."

"Something happened in her brain that made her snap," he told Inside Edition in 2018.