Throwing down the gauntlet: Cornwell challenges critics over serial killer

Patricia Cornwell takes out full-page advertisement to challenge her critics over Jack the Ripper theory

By taking out a full-page advertisement in today's Independent, containing an open letter challenging her doubters, Cornwell may appear to be playing into the hands of those who say her determination to prove Sickert's guilt is obscuring some of the key facts of the notorious murders.

The surprise move is likely to fuel the controversy surrounding her theory and baffle many of the admirers who have made Cornwell one of the most well-paid and widely read crime writers in the world. The advert, which appears on page 21, attacks the art experts and Ripper enthusiasts who said earlier this week that her case against Sickert was inconclusive and based on a mis-reading of the evidence.

Her decision to place the advertisement is believed to have surprised her media advisors, aware that it could backfire and undermine her credibility.

The criticisms, reported in The Independent on Tuesday, followed the disclosure that Cornwell had returned to London to conduct more tests on documents linked to the Ripper case. She is preparing a new edition of her 2002 book Portrait of a Killer in which she sets out her conclusions that Sickert was the Ripper, who murdered and mutilated five women in the East End in 1888.

Cornwell writes: "My investigation is far from an obsession but an opportunity to provide a platform for applying modern science to a very old, highly visible case in the hope that we might learn something that could help solve modern crimes."

Despite the book's subtitle, Jack the Ripper: Case Closed, Cornwell does acknowledge in her letter that "the case is far from closed", although she stands by her conclusions that Sickert is the Ripper. She says she has a duty to investigate any new evidence and challenges her critics to back their attacks with "scientific, investigative and historical fact".

Cornwell's case against Sickert, a painter who followed the Impressionist school, was that there were similarities between mitochrondrial DNA on Sickert's correspondences and on some of the hundreds of letters sent to the police at the time, claiming to be from the Ripper. Most are assumed to be hoaxes. Cornwell also claims that Sickert dropped clues in his paintings, some of which were of murder scenes and that a sexual dysfunction made him anti-women. Her return to London is believed to involve an attempt to match fingerprints on the Ripper letters with Sickert's.

Cornwell, a former journalist, spent $2m (£1.1m) buying more than 30 Sickert paintings and paid for forensic experts to conduct the scientific work.

Her critics include Matthew Sturgis, whose biography of Sickert was published this year and contained a postscript denying the Cornwell claims. Sturgis told The Independent he believed Cornwell saw herself as a "fearless girl reporter" attempting to solve the mystery after years of male incompetence. Other critics include Richard Shone, Sickert expert and editor of The Burlington Magazine, and other Ripper enthusiasts, who say her evidence is inconclusive and at the most suggests Sickert could have written the letters. All refute her belief that Sickert was in London at the time of the killings.

Stephen Ryder, a US-based "Ripperologist", said the author was like a number of other people who took an interest in identifying the Ripper: "They get tunnel vision on one suspect which overshadows all the other evidence to the contrary. I don't favour one suspect over another."

Her advertisement is believed to be the first time a serious author has taken such a step to get their point across.