Kelly Renée Brookshire was born on March 8, 1968, in Lawrenceville, Georgia, into a poor cotton-farming family. According to court documents, she endured sexual abuse by her stepfather and other men during her childhood and adolescence. During her senior year of high school, she reported being date-raped, resulting in the birth of her first son nine months later. 

In 1987, at the age of 19, Kelly married her first husband, Jeff Banks; their marriage lasted six months. She married Douglas Gissendaner for the first time on September 2, 1989. The couple had a child together, faced financial hardships, and eventually divorced in 1993. Kelly remarried Douglas in May 1995, and by December 1996, they had purchased a home together in Auburn, Georgia. In addition to her daughter with Douglas, Kelly had two sons, making Douglas the stepfather to her children. ​

On February 7, 1997, Kelly Gissendaner conspired with her lover, Gregory Bruce Owen, to murder her husband, Douglas Gissendaner. That evening, Owen hid near the couple's home in Auburn. When Douglas arrived, Owen forced him into his car at knifepoint and drove him to a wooded area in Gwinnett County near Harbins Park. After striking Douglas in the head with a nightstick, Owen stabbed him multiple times in the neck and back. Kelly arrived at the scene shortly after; together, they set fire to Douglas's car and concealed his body in the woods. ​

Prosecutors argued that Kelly orchestrated the murder to remove Douglas from her life while benefiting financially from his life insurance policy and retaining their shared house. Owen testified that Kelly believed murder was the only solution, as she thought Douglas "wouldn't leave [her] alone by just divorcing him." ​

Before the trial, prosecutors offered both Owen and Kelly plea deals of life imprisonment without the possibility of parole for 25 years. Owen accepted the deal, pleaded guilty, and testified against Kelly, resulting in his life sentence. Kelly rejected the plea offer and was subsequently convicted of malice murder on November 18, 1998. She was sentenced to death on November 20, 1998. ​

While incarcerated, Kelly underwent a religious transformation, engaging in theological studies and ministering to fellow inmates. Despite appeals for clemency from various supporters, including her children and Pope Francis, the Georgia Board of Pardons and Paroles denied her clemency. Kelly Gissendaner was executed by lethal injection on September 30, 2015, at the Georgia Diagnostic and Classification Prison. She was the first woman executed in Georgia since 1945. ​