The US Supreme Court has refused a last-minute appeal by a female convict diagnosed with borderline mental retardation for a stay of her execution.

Teresa Lewis was found guilty of plotting to kill her husband and step-son in 2002 for life insurance money.

The court said in a ruling on Tuesday that the stay of execution request by the 41-year-old woman "is denied."

The ruling means that she will be executed by lethal injection on Thursday, September 23, becoming the first woman to be put to death in Virginia since 1912.

Lewis has admitted to hiring two accomplices for the murders, but has denied pulling the trigger.

Doctors, meanwhile, have said that she was not intelligent enough to mastermind the murders.

Virginia Governor Bob McDonnell, however, said that he could find "no compelling reason to set aside the sentence that was imposed by the Circuit Court and affirmed by all reviewing courts."

Lewis is the first woman to be executed in the United States since 2005.

Human rights groups have described her conviction as 'unsubstantiated.'

Amnesty International, for its part, has called on US officials to commute the death sentence of Lewis.

The controversial case is reportedly not the first and will not be the last one in the US to draw fire over what has been described as "a mockery of justice."