For nearly five decades, police and amateur sleuths have sought the identity of the Zodiac—and never come close to making an arrest. The serial killer who murdered at least five people, taunted police and terrorized Bay Area residents in the 1960s and 1970s apparently vanished without a trace. Yet he left behind a mystery that still grips the public imagination, spawning books, movies, TV crime shows, websites—and a trail of tangled theories.

Over the years, Zodiac buffs have suggested dozens of possible suspects based on speculation and circumstantial evidence. Conspiracy theorists have fingered Unabomber Ted Kaczynski, Wichita’s BTK Killer or members of Charles Manson family. A handful of publicity-seekers claim their fathers were the Zodiac. In recent years, absurd allegations have spread on social media—including that Texas Senator Ted Cruz was the Zodiac, even though he was born two years after the first confirmed killings.

“The level of crackpottery in the Zodiac case is stunning,” says Michael Butterfield, a writer who has spent 20 years researching the case and runs the website zodiackillerfacts.com. “Most of the people we refer to as suspects aren’t really suspects at all—just somebody that someone accused whose name got repeated online, even though there was never anything there.”

Here are eight who have generated the most interest:

Why Suspected: Kane worked in the same Lake Tahoe hotel as Donna Lass, who disappeared in 1970 and may have been another Zodiac victim. He served in the Naval reserves, where he might have learned coding, and a 1962 car accident left him with a brain injury that could have compromised his ability to control urges. He was arrested for peeping in 1961 and for prowling in 1968.

A retired police detective investigating the case in the 1980s claimed that Kane’s name was embedded in one of the Zodiac’s ciphers, and that Darlene’s sister Linda had identified a photo of Kane as the man she said had bothered Darlene at a restaurant. A San Francisco police officer who probably saw the Zodiac moments after Stine’s murder said Kane’s photo was closer than any other likeness he had seen. Kathleen Johns, who escaped from a man believed to be the Zodiac in Modesto in 1970, also identified a photo of Kane as the abductor.

Why Suspected: The 1966 murder of Cheri Jo Bates in Riverside, Ca. bore many similarities to the Zodiac killings. Staffers at the Riverside City College library, near where Bates’s body was found, said a coworker, Ross Sullivan, had made them uncomfortable and disappeared for several days after the murder. Sullivan also sported a crew cut and glasses similar to the composite sketch of the Zodiac. He moved to northern California in 1967 and was hospitalized several times for bipolar disorder and schizophrenia.

Sullivan wore an Army jacket and military-style boots like those that left footprints at the Lake Berryessa stabbings. Zodiac buffs also note that his letters mention “The Mikado,” by Gilbert and Sullivan, which could be a reference to Sullivan’s name.

Why Suspected: Portrayed as the prime suspect in Robert Graysmith’s books, one of which was the basis of the 2007 movie, “Zodiac,” Allen was questioned by police in 1969 and again in 1971 after a friend told authorities Allen had talked about wanting to kill people and secure a flashlight to a firearm, as the Zodiac did.

Allen wore a Zodiac-brand watch, owned the same caliber gun used in one Zodiac shooting and told police the bloody knives in his car were used for killing chickens. He was less-than honorably discharged from the Navy and been fired from his school-teacher job amid sexual-misconduct allegations. He was also ambidextrous, which some theorists say could have helped disguise his handwriting.

Police investigated Allen again in 1991 after an informant facing armed-robbery charges said Allen had boasted to him about killing a cab driver. At that point, Michael Mageau, who survived the Vallejo attack, identified a photo of Allen as the shooter. In the 2007 movie, victim Darlene Ferrin’s sister Linda also identified a photo of Allen as the man she said had stalked her sister. According to the film, police were closing in when Allen died.

Why Ruled Out: “Allen seems like a good suspect as long as you only get information from people who think he’s guilty,” says Butterfield. Allen didn’t match witness descriptions of the Zodiac. His fingerprints didn’t match those found in Paul Stine’s cab and believed to be the Zodiac’s. His palm print didn’t match one found on a Zodiac letter and his DNA didn’t match the partial DNA profile created in 2002 from saliva on an envelope believed to be the Zodiac’s. Two searches of Allen’s home found no incriminating evidence. Police had samples of his right and left handwriting and neither matched the Zodiac’s.

The 2007 movie contained many fictitious elements, Zodiac researchers say. Police considered Mageau’s photo ID to be weak and movie the scene with Darlene’s sister never occurred. Allen died of a heart attack in 1992.

Why Suspected: Marshall, a ham radio operator and movie projectionist, lived in Riverside in 1966 and in later in San Francisco near where Stine was murdered. Visitors to his home told police they found him peculiar and that he had talked about finding ”something much more exciting than sex.” Marshall liked old movies, including “The Red Phantom,” which was mentioned in a 1974 Zodiac letter. He lived in a basement apartment, which the Zodiac also cited. He owned a typewriter and a teletype similar to those the Zodiac used. They both liked felt-tip pens and odd-size paper.

Why Ruled Out: In a 1989 TV interview, Marshall conceded there were many similarities but denied being the Zodiac. Napa County sheriff’s detective Ken Narlow, who pursued the case for decades, said “Marshall makes good reading but not a very good suspect in my estimation.” Marshall died in a nursing home in 2008.

Why Suspected: Gaikowski edited a counter-culture newspaper in San Francisco. A former coworker sent long, rambling letters to law-enforcement agencies accusing him of being the Zodiac and said Gaikowski invited him to engage in violent acts together. The accuser, nicknamed “Goldcatcher,” appeared in disguise on an episode of the HISTORY Channel’s “MysteryQuest” in 2009 and provided recordings of Gaikowski’s voice. On the show, a police dispatcher who spoke to the Zodiac said she thought it was the same voice. Researcher Tom Voigt also notes that “Gyke” appears in a part of a cipher the Zodiac said contained his identity.

Why Ruled Out: “Goldcatcher” was a known conspiracy theorist with little credibility, described by a San Francisco police inspector as “one of the three top Zodiac kooks.” When Narlow, the Napa detective, interviewed Gaikowski, the journalist claimed he was out of the country at the time of the 1968 murders on Lake Herman Road, but had lost his passport. San Francisco and Napa police denied requests to compare a DNA sample from Gaikowski with the Zodiac’s. He died in 2004.

Why Suspected: In his 2014 book, “The Most Dangerous Animal of All,” Gary Stewart made a case that his biological father, Earl Van Best Jr., was the Zodiac. Stewart said Best resembled the composite sketch of the Zodiac, lived in California at the time of the killings, was interested in ciphers, knew a Satanist and a Manson-family member and liked Gilbert and Sullivan. Best also served time in prison for the statutory rape of Stewart’s mother and may have held a grudge against San Francisco Chronicle reporter Paul Avery, who wrote a series of articles about the couple.

Stewart claimed to have found Best’s initials in the Zodiac ciphers, and a document examiner said the handwriting on Best’s marriage certificate matched the Zodiac’s. Although their fingerprints didn’t match, a mark that could have been a scar was visible in Best’s and those found in Stine’s cab.

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Why Ruled Out:** Despite the vast publicity Stewart’s book received, experts quickly dismissed most of its claims. The method he used to crack the cipher was questionable; the fingerprint mark was similar to the Zodiac’s only if it was reversed and the handwriting on the marriage certificate was the minister’s, not Best’s. As for Best’s resemblance to the composite sketch, Butterfield says, “a crew cut with horned-rim glasses was hardly a unique look in the 1960s.” Best died in 1984.

Why Suspected: Dennis Kaufman also received extensive publicity claiming that his late stepfather, Jack Tarrance, was the Zodiac. Kaufman said Tarrance was a dead-ringer for the composite sketch and claimed to have a stash of incriminating evidence, including a roll of film depicting possible victims and a bizarre hooded costume like one the Zodiac wore during the Lake Berryessa stabbings. On a 2007 Discovery Channel documentary, a document examiner said Tarrance’s handwriting matched the Zodiac’s.

Why Ruled Out: Law-enforcement officials dismissed Kaufman’s evidence as nonsense. One photo showed a blob of color he claimed was Black Dahlia victim Elizabeth Short. The hooded costume Kaufman produced was much cruder than what the victims described. Researchers also challenged the document examiner’s credibility; she believed Tarrance had also written the JonBenet Ramsey ransom note. Tarrance died in 2006.

Why Suspected: The hooded man who stabbed the couple at Lake Berryessa said he had just escaped from a prison in Montana, according to Bryan Hartnell, who survived the attack. Researcher Kevin Robert Brooks developed a lengthy circumstantial case implicating Donald Lee Bujok, who was released in 1968 from Montana’s Deer Lodge Penitentiary after serving 11 years of a life sentence for killing a sheriff’s deputy.

According to Brooks, fellow inmates said Bujok had talked about killing people to make them slaves in the afterlife, as mentioned in a Zodiac letter. Brooks claimed the Halloween card sent to reporter Paul Avery depicted harsh conditions at the prison and that “Boo!” on the inside referenced Bujok’s name. Bujok had been discharged from the Army for mental-health reasons; Brooks alleged that markings on some Zodiac envelopes spelled out ‘Zodiac is a veteran with 4F.” Brooks also speculated that the Zodiac’s signature crossed-circle symbol was inspired by the helicopter landing pad at Fort Ord, California, where Bujok had been stationed.

Why Ruled Out: Bujok’s fingerprints did not match those believed to be the Zodiac’s. A park ranger at Lake Berryessa claimed Hartnell said the prison was in Colorado, not Montana. Bujok was released just three days before the Zodiac’s Lake Herman Rd. killings; some researchers think he would have had difficulty traveling across three states in that time. Bujok was incarcerated during the Bates murder and other early killings that may have been the Zodiac’s. He died in 1993.