JK ROWLING has caused another literary stir after being exposed as the author behind a new crime novel.

But like any author of a thriller she should have known it is usually the fingerprints that give the mystery away.

And it was Ms Rowling’s telltale literary “fingerprints” that allowed Professor Peter Millican – a philosophy don at Hertford College in Catte Street – to unmask her pseudonym of Robert Galbraith, the ‘debut’ author of The Cuckoo’s Calling.

Prof Millican developed software called Signature to analyse and compare the “fingerprints” in text.

He said: “It reads through a text and can look for words that are particularly frequent or ones which are particularly unusual and it finds particular phrases which are very distinctive of a particular author.

“The other thing you can do is look for frequencies of other words, such as how many times the author uses ‘the’, so you can do it on a relatively small amount of text.

“What the software does is to plot the various authors on a graph and indicates how far they are apart. It turned out to my surprise that JK Rowling was closest.” Prof Millican, who is launching a new degree programme combining computer science and philosophy, said that he was approached by The Sunday Times last Friday.

He was told the paper already suspected Rowling to be the author behind The Cuckoo’s Calling and wanted him to prove it.

He compared it to eight other texts.

He said: “The Casual Vacancy and Harry Potter and the Deathly Hallows ended up closer than the others quite a high proportion of the time, almost on every test I did.

“That was a bit of a surprise given that the genre of the other works were detective novels.

“I found it quite striking.

“But it is quite hard to know how distinctive her writing style is and it is difficult to give examples of JK Rowling’s style because the software shows patterns which are relatively subtle.”

Prof Millican hit the headlines in 2008 when he was asked by a Republican to prove that United States President Barack Obama did not write his autobiography Dreams From My Father, and that it was written by a former terrorist, Bill Ayers.

Prof Millican said: “I found it was most unlikely he did write it because there were significant differences in his use of language.”