A woman convicted of the brutal murder of a mentally disabled man is poised to become only the 14th female to be executed in the United States since 1976 on Wednesday when she faces death by lethal injection in Texas.

Barring a successful last-ditch appeal, Suzanne Basso, 59, will be executed by lethal injection at 6:00 pm local time (0000 GMT Thursday) at Huntsville Prison in Texas.

The wheelchair-bound killer, who weighed 350 pounds (160 kilograms) at the time of her arrest in September 1999, was sentenced to die for the horrific killing of Louis "Buddy" Musso" in 1998, whom she killed in an attempt to benefit from his life insurance.

Musso was burned with cigarettes and beaten with belts, baseball bats and hobnailed boots by Basso and five others.

His body, bloodied and battered beyond recognition, was found dumped in a roadside ditch in Houston in August 1998, according to court documents.

Despite a series of appeals which led all the way to the US Supreme Court, Basso's death sentence has been reconfirmed over the years, meaning she will be executed in Wednesday unless the Texas board of parole decides otherwise.

Anti-death penalty advocates have condemned Basso's looming execution however, on the grounds that her physical and psychological state -- she has shown signs of suffering from mental illness -- mean she poses no threat to society.

"The primary criterion for imposing the death penalty in Texas is that the defendant is deemed to be a 'future danger' to society," said Richard Dieter of the Death Penalty Information Center.

"It is hard to see how this 60-year-old woman, confined to a wheelchair, would be a threat to society if she remained in prison for the rest of her life.

"She has exhibited multiple signs of mental illness, which may have played a role in her crime. Texas has many far more dangerous criminals serving time in prison. Executing Suzanne Basso appears both unnecessary and unjustified."

Execution of women still rare

Basso, whose attorneys have also argued she is mentally disabled, will become only the 14th woman to be executed, and the fifth in Texas, amongst the 1,366 executions carried out since capital punishment was reinstated in the United States in 1976.

"The numbers are very small because generally women do not often commit the kind of aggravated murder for which the death penalty is sought," Dieter said.

The numbers of women sentenced to death and facing execution on death row continues to remain small compared to their male counterparts, according to the DPIC.

There have been only 571 recorded executions of women since the first in 1632. That represents just under three percent of the total executions carried out since 1608.

Joan Howarth, a professor of law at Michigan State University, has written that the execution of women "is troubling because capital punishment should protect innocence (and weakness, which is generally feminine.)"

"Capital punishment is usually men killing men," Howarth added in a 2002 paper for the Oregon Law Review.

"Putting someone to death is masculine work, whoever does it. Being put to death is overwhelmingly man?s work too, but some women have been found fit for the role throughout history."

The last woman to be put to death in the United States was Kimberly McCarthy, 52, who was executed in Texas in June last year for the brutal murder of an elderly lady.