Her cause of death was not immediately known.
Jarmon, 34, was accused of fatally shooting 77-year-old Charles Hugh Perkins on April 29, 2016, in the yard of Perkins’ home. The men lived next door to one another.
The Times-Daily reported that witnesses testified they saw Jarmon shove the elderly man before grabbing his hand and pulling a gun. Jarmon shot Perkins in the head.
Jurors, who told the trial judge on Friday that they could proceed without Darby, deliberated for about 30 minutes before finding Jarmon guilty of murder, the newspaper said. Lauderdale County Judge Gil Self appointed attorneys to represent Jarmon in Darby's place.
Jarmon faces life in prison when he is sentenced in December.
Colleagues mourned the loss of Darby, who was described as a humble woman who did her best to serve others.
District Judge Carole Medley, who was at the hospital awaiting Darby's test results before her death, described her as "one of the most well-respected and well-thought-of attorneys in (the Florence) area."
"She worked extraordinarily hard to be sure anybody she represented had all the rights the law allows," former prosecutor and Judge Mike Jones told the Times-Daily.