Kenneth Eugene Smith was born on July 4, 1965, in Alabama, United States. 

On March 18, 1988, Kenneth Eugene Smith, along with John Forrest Parker, murdered Elizabeth Dorlene Sennett in her home in Colbert County, Alabama. Smith and Parker had been hired by Billy Gray Williams, who was working under the orders of Reverend Charles Sennett, Elizabeth's husband, to carry out the killing. The payment for the murder had been set at $1,000 for each man.

The plan unfolded when Smith and Parker arrived at the Sennett home, claiming they were there to survey the property for hunting. Elizabeth called her husband, who told her to let them in. Charles Sennett had given the men money to buy a weapon, but they spent it on drugs instead. They did not bring a firearm and opted to use a six-inch survival knife and other objects found in the home.

While Parker asked to use the bathroom, Smith attacked Elizabeth. He began to beat her with various items, including a fireplace set, a walking cane, and a pipe. Parker soon joined in, and after beating her, they stabbed Elizabeth multiple times with the knife, ultimately causing her death.

Sheriff Ronnie May arrived at the scene soon after the attack and initially could not find a pulse. However, emergency medical technicians later did. Elizabeth was taken to the hospital, where she was declared dead. The investigation soon revealed that the scene had been staged to look like a robbery. Eventually, authorities received tips that led them to the names of the suspects involved in the murder.

In the following days, Charles Sennett was questioned by police but denied involvement. However, he later confessed to his sons that he had orchestrated the murder and then subsequently took his own life. Investigators searched Smith's home and found evidence linking him to the crime, including a stolen video recorder from the Sennett residence.

After two trials, Smith was convicted of capital murder. He was sentenced to death initially in 1989, but that conviction was overturned in 1992. In a second trial in 1996, he was again sentenced to death, despite the jury recommending a life sentence. Smith remained on death row for many years until legal proceedings led to his execution.

Smith's first scheduled execution occurred on November 17, 2022. However, it was called off due to issues with the execution procedures. He was eventually executed by nitrogen hypoxia on January 25, 2024, marking the first time this method had ever been used for an execution in the United States. During the execution, witnesses reported that Smith appeared to be in distress, convulsing for several minutes before he was pronounced dead.

This execution raised many questions about the use of nitrogen gas as a method of execution and led to discussions about its potential ethical implications. Following Smith's execution, several other states considered implementing nitrogen hypoxia as an execution method.