Gibbs was born in Georgia on Christmas Day 1932. She operated a daycare from her home and was a dedicated member of the local church community. She had been married to her husband Marvin for 18 years before she began killing.

In 1965, Gibbs committed her first murder, poisoning her husband Marvin by putting arsenic into his dinner. Whilst he was unwell in hospital, she brought him homemade soup containing yet more poison. After Marvin’s death, doctors decided the cause of death had been a liver disease. After her husband’s death, Gibbs was supported by the local church community. She later donated some of her husband’s life insurance money to the church.

Eight months after the death of Gibbs’s husband, she poisoned her youngest son, also named Marvin. He was assumed to have inherited a liver disease from his father although his death certificate listed hepatitis. Gibbs was not suspected of any wrongdoing and she again donated a large portion of her life insurance payout to the local church. In January 1967, another one of Gibbs’s sons, 16 year old Lester, died suddenly. Doctors listed his cause of death as a rare muscular disorder and for a third time, Gibbs donated life insurance money to the church.

Gibbs was initially found mentally unfit to stand trial and was confined to a mental institution where she worked as a cook. Later, however, she did stand trial and was sentenced to five life sentences. She remained imprisoned until 1999 when she was diagnosed with Parkinson’s disease and was released into the custody of her sister. She died in 2010 in a nursing home in Douglasville, Georgia.