Kenneth Bianchi was born on May 22, 1951, in Rochester, New York. He was born to a 17-year-old mother who was an alcoholic and a sex worker. Two weeks after his birth, she gave him up for adoption. In August 1951, Nicholas Bianchi and his wife, Frances Scioliono-Bianchi, adopted him. Kenneth was their only child.

From a young age, Bianchi showed signs of trouble. His adoptive mother described him as a "compulsive liar" from the time he could speak. He often daydreamed and went into trance-like states. At the age of five, a physician diagnosed him with petit mal seizures. He also had an involuntary urination problem, which caused him embarrassment and led to frequent medical examinations.

Bianchi displayed many behavioral issues as a child. He was prone to fits of anger and had trouble sleeping. He frequently wet his bed. On January 2, 1957, he fell off a jungle gym and landed on his face, which further worried his mother. In an effort to change his behavior, she sent him to a private Catholic elementary school. She also took him to a psychiatrist multiple times. At the age of ten, Bianchi was diagnosed with a passive-aggressive personality disorder.

Despite being tested as having an above-average IQ of 116 at the age of eleven, Bianchi struggled academically. He was removed from school twice because he had difficulty getting along with teachers. His adoptive mother described him as "lazy."

In July 1963, when he was around twelve years old, Bianchi engaged in inappropriate behavior when he pulled down a 6-year-old girl's underwear. The difficulties in his life became more pronounced after the sudden death of his adoptive father from pneumonia in 1964. Bianchi did not show any visible signs of grief after his father's death. Following this, Frances had to work, and Bianchi attended public high school. She was known to keep him home from school for long periods.

Despite his challenges, Bianchi dated often and joined a motorcycle club while in his teenage years. He graduated from Gates-Chili High School in 1970. Soon after, he married his high school sweetheart, Brenda Beck. However, the marriage ended after just eight months, with Brenda leaving without an explanation.

As a young adult, Bianchi aspired to become a police officer. He enrolled at Monroe Community College to study police science and psychology but dropped out after one semester. Following this, he took on a series of low-end jobs, eventually becoming a security guard at a jewelry store. This job allowed him to steal items, which he would give to girlfriends or prostitutes to gain their loyalty. Although he applied to the sheriff's department, he was rejected.

In 1976, Bianchi moved to Los Angeles, California, where he began spending time with his older cousin, Angelo Buono. Bianchi admired Buono's flashy lifestyle and ability to attract women.

Kenneth Bianchi and his cousin, Angelo Buono, created a reign of terror in Los Angeles during the late 1970s. They targeted women and girls aged 12 to 28, convincing them that they were police officers using fake badges. They drove around in Buono's vehicles, which looked like retired police cars, equipped with flashing lights to help them deceive their victims.

Their first confirmed victim was Yolanda Washington, who was found on October 17, 1977. Her body showed signs of having been cleaned and had faint rope marks around her neck, wrists, and ankles. This pattern continued with many other victims. They would abduct women, then take them to Buono's home, where they would torture and murder them. Bianchi and Buono experimented with various ways to kill, often resorting to strangulation.

Judith Lynn Miller, a 15-year-old student, was next. She was murdered on Halloween, 1977, after being identified as a sex worker. Her body was discovered with her legs posed in a specific manner, revealing evidence of assault and strangulation.

Over the course of their crimes, Bianchi and Buono killed at least ten young women. They were not limited to one method of killing, often showing extreme brutality. For instance, Kristina Weckler, found on November 20, 1977, was tortured with Windex and then asphyxiated.

The killings continued until 1979, when Bianchi moved to Bellingham, Washington, at Buono's insistence. This change was prompted by Bianchi's fear of being caught, especially after he learned he was under investigation. In Washington, he committed two more murders on January 11, 1979. Bianchi murdered Karen Mandic and Diane Wilder in a house he was guarding.

After these murders, Bianchi was arrested, and he began to reveal details about his earlier crimes with Buono. His arrest brought attention to the previously unsolved Hillside Strangler cases. Despite his claims of multiple personalities, Bianchi was eventually diagnosed with antisocial personality disorder and sentenced to life in prison.

Throughout the investigation and trial, Bianchi tried to cooperate with law enforcement but ultimately faced charges for his role in the murders. He was sentenced to six terms of life imprisonment and remains in custody today.