A new book claims to have unmasked one of the most notorious serial killers, the Zodiac Killer who terrorized the San Francisco Bay Area in the 1960s and 70s, murdering at least seven people, terrorising the city and taunting the police and newspapers with cryptic notes and undecipherable cyphers and cryptograms.

It’s written by Louisiana businessman Gary L. Stewart and has the enticing title: “The most dangerous animal of all: Searching for my father and finding the Zodiac Killer.”

So enticing (the title refers to a letter the Zodiac wrote claiming ‘Man is the most dangerous animal of all’) that I picked up a copy and read it. And so have millions more, with the book earning a place on the coveted New York Times best-sellers list backed by a big name publisher, Harper Collins.  All of which lend kudos and credibility compared to the many alternative theories about who the Zodiac Killer may be.

Stewart tell the story of his father’s crimes in a “novelistic manner” and while it’s no ‘In Cold Blood’  events moves a long at a fair pace, and are neatly described with the help of journalist and crime writer Susan Mustafa.

The book begins in 2002 with Stewart, adopted at birth and now in his late 30s, the director of a Louisiana cleaning company, who receives a phone call from a woman called Judy, who says she is his birth mother.

They eventually meet in San Francisco, form a relationship and then the question about who his father was becomes something he must answer.

Judy is reluctant to tell him and for good reason. It later emerges that she fathered him at age 14 in 1962 after running away to Mexico City and later New Orleans with a manipulative, creepy man twice her age called Earl Van Best Junior or ‘Van’ as he was known. The case attracts media attention with the San Francisco papers calling it the “The Ice Cream Parlour Romance” because met Judy outside an ice-cream parlour when she got off the school bus.

We are told the story of Earl’s early life as the son of a highly respected army minister, but later forced to live with his mother, Gertrude, a cold, unloving adultress whose only contribution to her son’s development is to teach him to play the organ.

As an alienated, unhappy young man, Stewart narrates his father’s obsession with  13 year old Judy, his various arrests and imprisonments, his numerous trips to Mexico to obtain antique books and manuscripts to sell in San Francisco, his mingling with Satanist Anton LaVey’s harem in Haight Ashbury and his violent, spontaneous crimes, cryptic notes and games with the police and newspapers.

Stewart recounts the various disturbing murders as they have been told so many times before in books, true crime documentaries and movies, but using the chilling words “my father” when referring to the horrific stabbings and shootings.

He later discovers that Earl Van Best died in Mexico City in the 1994, choking on his own vomit and visits his unmarked grave. Here he makes a startling confession:

“I loved this man in some inexplicable way. He was my father. We were bound together by some invisible, unbreakable rope.“

Among Stewart’s reasons for thinking his father was the Zodiac are:

• his resemblance to the police identi-kit of the Zodiac Killer

• the army intelligence skills Van had learnt from his own father to create undecipherable ciphers
• his cruelty and criminality
• that his time and out of jail corresponded with the murders
• that the name “Earl Van Best Jr” can be found in the ciphers

• matches in the handwriting of ‘Van’ and the Zodiac letter, corroborated by a hand-writing analyst
• a scar on his father’s finger that appears to match that of a fingerprint taken off the Zodiac Killer

The book is quite convincing, not least because you’d wonder why anyone would wish to assert that their father is a notorious serial killer, unless they were fairly certain. Of course, there is also the lure of some kind of celebrity and the royalties earned from publishing a best seller.

But the one key piece of  evidence tha would prove Stewart’s claim beyond doubt, namely DNA matching, is missing.

(It is DNA matching which appeared to prove that Jack the Ripper  was a Polish immigrant called Aaron Kominski but this has since been disputed to an alleged error by the scientist)

Stewart writes of the many years he has battled to have the partial  Zodiac Killer DNA (taken off a stamp affixed to one of the taunting letter he sent out) compared with his own DNA to prove his father was the serial killer.

He claims a San Francisco police cover up has prevented this from ever being tested. The reason for the cover-up: his mother Judy’s marriage to ground-breaking homicide detective and later deputy mayor of San Francisco Rotea Gilford (the first black man to achieve both those positions), who worked on the Zodiac case and who died in 1998.

The SFPD, Stewart suggests, has stalled the testing to protect Gilford’s name  were it to emerge that he married the teenage bride of the Zodiac Killer.

As with Jack the Ripper, a veritable community of amateur sleuths and conspiracy theorists exists to weigh up the evidence and suggest theories about who the Zodiac Killer really was.

The most comprehensive website is zodiackiller.com, which recently celebrated its 16^th anniversary and claims to get 10 million hits a month. It’s run by Zodiac fanatic Tom Voigt. He gave Stewart’s book just one star in his review on Amazon.com, systematically dismissing any link Stewart has claimed between his father and the Zodiac Killer:

Stewart claims his father looks like the Zodiac – Voigt writes: “Open any high school yearbook from the 1960s and half of the males pictured will resemble the sketch of the Zodiac killer. It’s not “evidence” of guilt. Not impressed.”

Stewart says his father’s name is in the codes – Voigt’s response: “So is mine. So is yours. People have been finding what they were looking for in the codes for 45 years. This is nothing new. It’s not evidence” of guilt. Not impressed.”

(On this point, I have to confess, I have trouble understanding Stewart’s explanation for finding his father’s name in a Zodiac cryptogram.)

There are a dozen people who claim to know the identity of the Zodiac Killer. These include Dennis Kaufman who claimed that his stepfather Jack Tarrance was the Zodiac Killer, but whose claims were later discredited.

The most famous suspect is Arthur Leigh Allen a schoolteacher, named by former San Francisco Chronicle journalist Robert Graysmith in what is considered the best book on the murders, ‘Zodiac’.

Graysmith’s book formed the basis for the exceptionally disturbing and very good 2007 David Fincher movie. Arther Leaigh Allen denied all his life he was the Zodiac killer and his DNA was later found to not be a match for the partial DNA obtained from the stamp. (The DNA itself may be a red herring, as there is no proof the Zodiac Killer licked the stamp affixed to the envelope, something Stewart does admit to in his book.)

But Gary Stewart remains convinced that his father, Van, is the Zodiac as he writes at the end of the book:

 I have handed the SFPD their killer. I’ve given them motive, means, opportunity, a forensic handwriting match, identical scars, and my father’s name embedded throughout the Zodiac cyphers. And I have DNA profile of my father waiting for comparison.

The legion of Zodiac ‘experts’, disagree and why wouldn’t they, after all – what would they do, if the mystery was solved.