Kelly Gissendaner, 47, is set today to be the 16th woman executed since the Supreme Court re-established the death penalty in 1976.
She is currently the only woman on death row in the southern state of Georgia, where the minimum age for execution is 17. She is set to die by lethal injection.
Gissendaner was convicted in 1997 of conspiring with her lover to kill her husband.
The lover, who actually carried out the murder, negotiated a plea deal with prosecutors and was granted a life sentence with the possibility of parole after 25 years.
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"The outcome illustrates one of the fundamental flaws with the death penalty -- it's applied arbitrarily," said Steven Hawkins, executive director of Amnesty International, which is among a number of groups calling for her sentence to be commuted to life in prison.
On Wednesday, Richard Glossip, 52, is set to die by lethal injection in Oklahoma, a conservative midwestern state.
Glossip, who has proclaimed his innocence for the past 18 years, was granted a last-minute reprieve two weeks ago while the state's top court considered his appeal.
Glossip was convicted based on the testimony of fellow motel employee Justin Sneed, who pleaded guilty and was able to negotiate a life sentence by claiming his co-worker had masterminded the plot.
He also has garnered attention for his failed bid to ban a controversial drug used in lethal injections. The Supreme Court upheld the use of the drug midazolam in June, saying it does not violate the US Constitution.