Sedley Alley was born on July 30, 1955, in the United States. Details about his early childhood and upbringing are limited, but records indicate that he experienced personal struggles and instability throughout his life. Prior to the murder that led to his conviction, Alley had a history of alcohol abuse, which played a role in his erratic behavior. He lived with his wife on a military base in Tennessee while working various jobs. Alley reportedly had no prior homicide record before the 1985 crime that would place him on death row.

On the night of July 11, 1985, Sedley Alley abducted 19-year-old Lance Corporal Suzanne Marie Collins, a United States Marine stationed at Naval Support Activity Mid-South in Millington, Tennessee. Collins had been jogging on base when Alley lured her into his vehicle. He then drove her to nearby Edmund Orgill Park, where he viciously beat her, fracturing her skull, and subjected her to horrific torture. During the assault, Alley forcibly shoved a tree branch into her body with such force that it punctured her abdomen and tore a lung. Collins died from blunt force trauma and massive internal bleeding.

Two fellow Marines heard Collins’ screams during the abduction and later reported seeing a car that matched Alley's vehicle. This led military police to question Alley shortly after the crime, but at that time they did not detain him. The following morning, Collins’ body was discovered, prompting immediate suspicion of Alley. He was arrested on July 13, 1985, and initially claimed he had accidentally hit Collins with his car and killed her while trying to help. This story was disproven by the autopsy, which showed deliberate and violent assault. Alley later confessed to the murder, though he later recanted and alleged his confession was coerced.

On March 17, 1987, Sedley Alley was convicted of first-degree murder, aggravated kidnapping, and aggravated rape. He was sentenced to death on May 18, 1987, and received consecutive 40-year prison terms for the kidnapping and rape charges. Over the next two decades, Alley filed numerous appeals, citing issues with his confession and requesting DNA testing, but courts consistently upheld his conviction and sentence.

On June 28, 2006, after nearly 21 years on death row, Sedley Alley was executed by lethal injection at Riverbend Maximum Security Institution in Nashville, Tennessee. The execution lasted approximately seven minutes, and Alley was pronounced dead at 2:12 a.m.

Years after his execution, Alley's daughter and the Innocence Project petitioned for posthumous DNA testing, arguing that evidence from the crime scene might prove his innocence. Multiple courts denied these requests, leaving ongoing controversy surrounding his case. Despite these challenges, Alley remains legally recognized as the murderer of Suzanne Marie Collins.