Dennis Lynn Rader was born on March 9, 1945, in Pittsburg, Kansas. His parents, Dorothea Mae and William Elvin Rader, were hard-working folks—Dorothea as a bookkeeper and William at Kansas Gas Service. Dennis was the eldest of four boys and grew up in Wichita. He often felt neglected at home, especially by his mother, and this left him feeling bitter.

From an early age, Dennis harbored disturbing fantasies and began exhibiting harmful behaviors. He tortured small animals and acted out dark sexual fantasies involving bondage and voyeurism. He would even dress in women's clothing, stolen from neighbors, to spy on them, adding a layer of secrecy to his troubling activities. Despite these early warning signs, his unsettling habits remained hidden from those around him, allowing him to maintain an outward appearance of normalcy.

As he grew older, Dennis's life seemed to follow a conventional path. After a brief stint at Kansas Wesleyan University and serving in the United States Air Force, he married Paula Dietz in 1971, with whom he had two children. Dennis earned a degree in Administration of Justice and worked in security, where ironically, he installed alarms in homes of people concerned about the very crimes he committed. His roles in the community, including a dogcatcher and compliance officer, church president, and Cub Scout leader, belied his darker predilections, which resurfaced periodically. By the 2000s, as local memories of his earlier crimes began to fade, a renewed interest in his case prompted him to seek attention once again, leading to his eventual capture and arrest in 2005.

In January 1974, the Otero family of Wichita, Kansas, faced a horrifying tragedy. Joseph Sr., Julia, and their two children, Joseph Jr. and Josephine, were brutally murdered in their own home. The family's three older children made the grim discovery upon returning from school. Dennis Rader, later known as the BTK Killer, confessed to this heinous crime in 2005.

Rader's methodical approach to the killings is chilling. He cut the phone lines before entering the Otero residence, then forced the family to lie on the living room floor at gunpoint. After binding them, he suffocated Joseph Sr. with a plastic bag and strangled Julie. He then placed bags over the heads of the children, suffocating Joey and later hanging Josie in the basement.

His next victim, Kathryn Bright, was attacked in April 1974. Rader broke into her home but was surprised to find her brother, Kevin, present. After restraining Kevin, Rader attempted to strangle Kathryn before resorting to stabbing her when she fought back. Kevin survived by pretending to be dead.

In March 1977, Rader targeted Shirley Relford, whom he followed home. After tying up her children, he strangled Shirley while her children screamed nearby. Miraculously, the children managed to escape. 
Nancy Fox became Rader's next victim in December 1977. He entered her home, strangled her, and later called the police to report the murder.

Rader's craving for attention led him to send letters to the media, including one to KAKE-TV in 1978. He coined the name "BTK" and demanded recognition for his crimes. In response, the police attempted to communicate with him through a subliminal message on television but to no avail. 

In August 23, 2023, the Associated Press broke a chilling development regarding Dennis Rader, already infamous as the "BTK Killer." News surfaced pinning Rader as the primary suspect in two more brutal killings, this time in Oklahoma and Missouri. Authorities, digging into his past, stumbled upon what they described as "possible trophies" from his victims during a search at his former residence in Kansas. This discovery set off a fresh wave of investigations into Rader's potential involvement in a string of unsolved disappearances and murders.

One such case involved 16-year-old Cynthia Dawn Kinney, who vanished without a trace from Osage, Oklahoma, on June 23, 1976, after a routine visit to the Osage Laundromat. Witnesses recalled seeing her leaving the laundromat at 9:30 a.m., stepping into a faded beige 1965 Plymouth Belvedere. In 2023, Osage Sheriff Eddie Virden revealed that Rader had surfaced as a prime suspect. Investigators drew connections between Rader's past involvement with the Boy Scouts in the area and his use of the phrase "bad wash day" in his writings. Adding to the suspicion, a bank across the street from the laundromat had new ADT alarms installed around the time Kinney disappeared, a job Rader had as a regional installer for ADT.

By 2004, the investigation into the BTK Killer had gone cold. But then, something changed. Rader started sending messages to the local media. This ultimately led to his arrest in February 2005. In March 2004, The Wichita Eagle got a letter from someone using the name "Bill Thomas Killman". The letter claimed responsibility for Vicki Wegerle's murder in 1986. The enclosed photos and stolen driver's license were crucial evidence. DNA under Wegerle's nails gave police new leads. They tested over 1,300 men's DNA. 

In May 2004, KAKE got a letter with a story outline and a word puzzle. In June, a gruesome package with details of the Otero murders was found. In July, a false claim about another death emerged. Rader later confessed he was planning another kill for October 2004. Packages continued, including one with threats to a detective's life in October and another with Nancy Fox's license in December. In January 2005, Rader tried leaving a box in a truck but failed. In February, more postcards came. Then, Rader sent a floppy disk to a TV station, which contained crucial evidence leading to his arrest.

Rader was apprehended while driving near his Park City home around midday on February 25, 2005. When asked why he was being taken downtown, he responded calmly, "Oh, I have suspicions why." Authorities, including Wichita Police, the Kansas Bureau of Investigation, the FBI, and ATF agents, conducted searches of Rader's residence and vehicle. They confiscated various items, including computer equipment, a pair of black stockings found in a shed, and a cylindrical container. Additionally, locations like his church, City Hall office, and the Park City library were thoroughly examined. At a press briefing the following morning, Wichita Police Chief Norman Williams declared, "the bottom line: BTK is arrested.

On February 28, 2005, Rader faced charges of 10 counts of first-degree murder. Shortly after his arrest, an anonymous source claimed Rader had confessed to more murders beyond those known. However, the district attorney denied this, yet didn't confirm or deny Rader's confessions. On March 5, news sources claimed Rader had confessed only to the 10 murders he was charged with. On March 1, Rader's bail was set at US$10 million, and a public defender was assigned to him.

On June 27, the trial date, Rader pleaded guilty, describing the murders in detail without remorse. At his August 18 sentencing, Rader apologized in a lengthy speech likened to an awards speech by the prosecutor. He received 10 consecutive life sentences. In August 2005, he was transferred to El Dorado Correctional Facility. During the drive, he spoke casually but broke down upon hearing victims' families' statements on the radio. 

He's now in solitary confinement for his protection, with limited privileges. Investigations into unsolved cases yielded no further evidence against Rader, though it's believed he planned more attacks. Psychologist Robert Mendoza diagnosed him with various personality disorders. Mendoza's interview was used on NBC's Dateline, leading to legal issues later settled in 2007.