Theodore John Kaczynski (/kəˈzɪnski/ kə-ZIN-skee; born May 22, 1942), also known as the Unabomber (/ˈjuːnəbɒmər/), is an American domestic terrorist and former mathematics professor.He was a mathematics prodigy, but abandoned his academic career in 1969 to pursue a primitive life.Between 1978 and 1995, he killed three people and injured 23 others in a nationwide bombing campaign against people he believed to be advancing modern technology and the destruction of the environment. He issued a social critique opposing industrialization and advocating a nature-centered form of anarchism.

The West Memphis Three are three men known for being convicted as teenagers in 1994, of the 1993 murders of three boys in West Memphis, Arkansas, United States. Damien Echols was sentenced to death, Jessie Misskelley, Jr. to life imprisonment plus two 20-year sentences, and Jason Baldwin to life imprisonment. During the trial, the prosecution asserted that the juveniles killed the children as part of a Satanic ritual.

The case generated widespread controversy and was the subject of several documentaries. Celebrities and musicians have held fundraisers to support efforts to free the men, who they say are innocent.

In July 2007, new forensic evidence was presented, and a report jointly issued by the state and the defense team stated: "Although most of the genetic material recovered from the scene was attributable to the victims of the offenses, some of it cannot be attributed to either the victims or the defendants."

Following a 2010 decision by the Arkansas Supreme Court regarding newly produced DNA evidence and potential juror misconduct, the West Memphis Three negotiated a plea bargain with prosecutors. On August 19, 2011, they entered Alford pleas, which allowed them to assert their innocence while acknowledging that prosecutors have enough evidence to convict them. Judge David Laser accepted the pleas and sentenced the three to time served. They were released with 10-year suspended sentences, having served 18 years.

John Wayne Gacy (March 17, 1942 – May 10, 1994) was an American serial killer and sex offender known as the Killer Clown who assaulted and murdered at least 33 young men and boys. Gacy regularly performed at children's hospitals and charitable events as "Pogo the Clown" or "Patches the Clown", personas he had devised. He was also active in his local community as a Democratic Party precinct captain, and building contractor.

The Zodiac Killer or simply Zodiac is the pseudonym of an unidentified American serial killer who operated in Northern California from at least the late 1960s to the early 1970s. The killer originated the name in a series of taunting letters and cards sent to the local Bay Area press. The letters included four cryptograms (or ciphers). Of the four cryptograms sent, only one has been definitively solved.

John George Haigh was a British serial killer active in the late 40's. He used to dispose of his victims' bodies by burning them in sulphuric acid, according to Forensic magazine. Haigh was convinced he was getting away with murder, literally, because he mistakenly thought that without a body there was no crime. His arrogance is what ultimately got him caught when he led police to the remains of his sixth and final victim, 69-year-old Olive Durand-Deacon.

While on trial, Haigh pleaded insanity and insisted to the court that he drank the blood of his victims. He was found guilty in 1949 and hanged a few months later.

French sisters Léa and Christine Papin worked as live-in servants for the Lancelin family in France in 1926. Although it was reported that they acted quite odd, never talking to anyone but themselves and showing little interest in anything besides each other, according to Historic Mysteries. They did their work quickly and lived with the family for almost seven years. Then, one night in February 1933, Mr. Lancelin, who had been waiting for his wife at a friend's house, came home to find her and their adult daughter dead on the floor in a pool of blood. Their eyes had been gouged out and faces smashed in. The Papin sisters were locked in their room and after getting a locksmith to open the door, the police said they found the sisters lying on the bed together with a bloody hammer nearby, according to The Vintage News. The Papin sisters immediately confessed to the crimes. While in prison, Christine became very distressed from being away from her sister and was eventually granted permission to see Léa. Reports said that the sisters seemed to be unnaturally close to each other, with some suggesting a sexual relationship, though doctors who examined the Papin sisters denied evidence of that.

A few months later, Christine suffered a mental breakdown and tried to gouge out her own eyes. After their trial, Christine was sentenced to life in prison for being the mastermind behind the murders, while Léa was eventually released from prison in 1943 and managed to get a job at a French hotel under a new identity. It is believed that she died in 1982, but that has never been confirmed.