Velma Barfield was a widow who used strychnine and arsenic to despatch her unsuspecting victims.

In 1974 in Fayateville, North Carolina, her mother Lillian Bullard was the first to succumb, secretly killed by strychnine in her Christmas dinner.

Two years later Barfield went to work caring for an elderly couple, Montgomery and Dollie Edwards.

Both died within a month of each other after experiencing severe stomach pains and vomiting. Their deaths were mysterious, but no crime was suspected.

The next year Barfield became carer to 76 year old John Henry Lee. He soon developed crippling stomach pains and died.

This time there were suspicions. Barfield was interviewed by police and confessed.

As a result police decided to exhume the body of her former husband, Jennings Barfield, who had died after less than a year of marriage. Tests proved he had been poisoned with arsenic.

A former boyfriend, Rowland Taylor, had died unexpectedly in 1978. His body was exhumed, and he too was found to have arsenic in his system.

Barfield was executed by lethal injection in 1984, the first woman to be given the death penalty after it was reinstated in the USA in 1976.