Hill's legal team had appealed to the nine justices to intervene on the grounds that the same court prohibited executions for "mentally retarded" prisoners – as called in US jurisprudence – in 2002.
Of the 38 states with capital punishment, 13 prohibit execution of a mentally retarded convict.
On Tuesday, Gov. Jeb Bush of Florida signed a bill prohibiting execution of mentally retarded prisoners.
Ebrahimi, who shot dead her husband while he was sleeping, faces imminent execution, despite international laws prohibiting execution for crimes committed by juveniles.
But Gov. Rick Perry vetoed a bill prohibiting execution of the retarded, and life without parole is not permitted as a sentencing option.
Since then, however, 11 additional states, including New York, have adopted laws prohibiting execution of the retarded, who are generally defined as people with I.Q.'s below 70.
He was unable to gain the agreement of Justices Sandra Day O'Connor or Anthony Kennedy, who were part of the majority in prohibiting execution of the retarded.
But when the court ruled that the Eighth Amendment prohibits execution of the mentally retarded, it made plain that states cannot weaken that protection with an unfair procedural standard.
The House voted 82 to 54 on Saturday to prohibit executions for two years beginning on July 1.
Both IHL and international human rights law – which continues to apply at all times – protect all detainees, strictly prohibiting executions, torture and other abuse.
In 1989, the court refused to prohibit executions of the mentally retarded under the Eighth Amendment, and throughout the 1990's it was hardly inclined to question the constitutionality of capital punishment.
