Lynda Cheryle Lyon was born on February 8, 1948, in Orlando, Florida. She was the daughter of Francis Stephen "Frank" Lyon and Berylene Elisabeth Owen. Lynda had a younger sister named Denyce, who was born in 1952. When Lynda was ten years old, her father passed away due to heart failure. This event deeply affected her family.

Lynda's relationship with her mother was strained. Lynda claimed that her mother was both physically and mentally abusive, which made their connection difficult. Due to these family issues, Lynda's early life was challenging.

In 1983, Lynda married an 80-year-old man named Karl Block, who was a military veteran. Lynda and Karl eventually divorced in December 1991. After her marriage to Karl, she married George Sibley, who was born on September 8, 1942. George described Lynda as someone who had a strong sense of charity.

While living in Key West, Florida, Lynda became active in her community. She served as the Secretary of the Humane Society and worked as an animal abuse investigator. Lynda also participated in civic activities. She was the president of the Friends of the Library for two years and worked as a publicity director for a mayoral candidate. Before her involvement in criminal activities, Lynda published a political magazine called Liberatis. 

On October 4, 1993, Lynda Cheryle Lyon Block and her common-law husband, George Sibley, were in a parked car outside a Walmart in Opelika, Alabama, with Block's nine-year-old son. A passerby noticed the boy looked distressed and alerted the police. Opelika Police Sergeant Roger Motley approached Sibley's car and asked for identification. Sibley argued that he did not need to show a license. As the situation escalated, Sibley drew a gun and began shooting at Motley, who returned fire and injured Sibley.

During the altercation, Block, who was at a payphone, heard the gunfire. She grabbed a gun and ran towards the scene. Witnesses reported that she was crouched down when she fired her weapon. Block fired at Sergeant Motley as he turned to face her, hitting him in the chest. Motley, who was not wearing a bulletproof vest that day, sustained fatal injuries.

After the shooting, both Block and Sibley claimed they acted in self-defense. They were part of an anti-government movement and had renounced their citizenship. They refused to cooperate with their legal representation, arguing that Alabama had no authority over them. Although it was unclear who fired the shot that killed Sergeant Motley, they were both convicted of capital murder.

Block was sentenced to death and entered death row on December 21, 1994, at Julia Tutwiler Prison for Women in Wetumpka, Alabama. Block was executed by electrocution on May 10, 2002, at Holman Correctional Facility. Before her execution, she had visits from friends and a spiritual adviser. She did not request a last meal or make a final statement. The execution took place shortly after midnight, and she was pronounced dead at 12:10 a.m.

Sibley later filed a petition claiming that Block had fired the shot that killed Motley. He was executed by lethal injection on August 4, 2005.