A British businessman says he knows the identity of Jack the Ripper thanks to a shawl he bought at an auction in 2007.

Russell Edwards, author of Naming Jack the Ripper, says DNA evidence proves Polish immigrant Aaron Kosminski was the notorious serial killer.

The shawl Edwards purchased was found near the body of Catherine Eddowes, the fourth victim of Jack the Ripper.

He had the shawl tested by experts at Liverpool John Moores University.

"We were looking at what the stains actually were, so we were testing for blood using conventional methods, and then also using different crime lights to pinpoint what the stains are," Jari Louhelainen, a senior lecturer of molecular biology, said in a video promoting Edwards' book. "We had some stains that were consistent with sperm stains."

He said the DNA extraction was quite difficult because the samples were very old.

Edwards said they had to find a female descendent of Jack the Ripper to positively identify the man who killed at least five women in London in 1888. They were able to find a woman who was a descendent of Kosminski's sister.

Kosminski died at the age of 54 in an asylum, Edwards said.

Edwards, 48, told The Guardian newspaper he has spent 14 years studying the cases and said the evidence presented in his book solidly identifies Jack the Ripper.

"Only non-believers that want to perpetuate the myth will doubt. This is it now -- we have unmasked him," Edwards said.

The book will be released in Canada on Tuesday.