The successful US author has spent years and a considerable amount of money trying to establish the murderer's identity. In her 2002 book -- Portrait of a Killer, Jack the Ripper: Case Closed -- she purports to have "exposed" the 19th century killer as artist Walter Sickert.

Her theories have been questioned by Ripper experts, including American Stephen Ryder, who describes her claims as "largely inaccurate." Authors of books on Sickert, such as Richard Shone and Matthew Sturgis, also reject her allegations. In full-page advertisements thought to cost more than $20,000 each in The Independent and The Guardian, Cornwell challenged her critics to prove her wrong.

"My ongoing investigation is far from an obsession, but an excellent 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," Cornwell wrote in the ads, published in The Independent and The Guardian.