David Stephen Middleton was born on June 25, 1961, in Boston, Massachusetts. He was the only son of a police officer. Details about his early life are mostly unknown. At some point, he moved to Miami, Florida. There, he studied at a police academy. He applied for a job at the Miami-Dade Police Department and was accepted in 1981. He worked as a police officer in the Miami-Dade County area.

During his time as a police officer, Middleton became known in the community. He began to take on more responsibilities. However, this did not mean he led a trouble-free life. His personal conduct raised issues that would later affect his career. After a few years, he eventually left Florida. He then moved to Colorado and later to Nevada. In Nevada, he worked as a cable TV repairman.

David Stephen Middleton was involved in multiple cases of abduction and murder between 1993 and 1995.

On November 21, 1993, 18-year-old Buffy Rice Donohue disappeared after leaving her parents' house in Montrose, Colorado. She was last seen at a Safeway store. Her car was later found at a Walmart with her belongings inside, but she was nowhere to be found.

On August 8, 1994, Thelma Amparo Davila was reported missing after not returning home from work at Circus Circus casino in Reno, Nevada. Her remains were eventually discovered in April 1995 in Verdi.

On February 6, 1995, Katherine Powell, a respected teacher, was reported missing after failing to show up for work. Officers found her belongings at her home and learned that an unfamiliar car had been seen in her area. On February 11, Powell’s body was found in a trash bin, wrapped in a sleeping bag.

Middleton was later linked to these cases through an investigation. Detectives noted that he had done a TV installation at Powell's home and owned a truck similar to one seen by witnesses. They discovered a shotgun in Middleton's apartment, which led to his arrest.

Evidence collected during the investigations linked him to the murders of Powell and Davila, and he was charged with two counts of capital murder. During his trial, various pieces of evidence were presented, including items purchased with Powell's credit card. Despite his claims of consensual encounters, the jury found him guilty of all charges in September 1997.

As a result, Middleton was sentenced to death for the murders of Thelma Davila and Katherine Powell. He also received additional life sentences for other related offenses. As of February 2024, he remains on death row in Nevada.