A computer expert told the high court today why he believed two former Italian colleagues of WPP chief executive Sir Martin Sorrell were probably responsible for an internet hate campaign against him.

Peter Sommer made a forensic examination of the computer evidence on behalf of Sir Martin's legal team for the advertising boss's libel and privacy case, concerning a series of defamatory blogs and a "grossly offensive" image of Sir Martin and a female executive.

Mr Sommer told the high court in London today that there were a number of factors pointing to the involvement of Marco Benatti, WPP's former "country manager" in Italy, and his lieutenant Marco Tinelli.

The computer expert said it was "relatively unlikely" that a third party had used Mr Tinelli's laptop computer to create blogs and emails that libelled Sir Martin.

"It is my experience that people are far less likely to use another's laptop without specific invitation than, say, a desk-based workstation, simply because laptops appear to be more 'personal' or 'private'," he said in his witness statement.

He added that it was also significant that, in the course of a single evening, lists of email recipients and the offensive image had been transferred from the laptop to a memory stick. "The close proximity in timing suggests they were all done by the same person and the actual timing suggests after-hours activity, when unusual behaviour would surely have shown up."

Mr Sommer said that techniques used to conceal who had been responsible for creating the blogs and emails would not require what might be called "geek" skills.

A guidebook containing instructions for such techniques, The Handbook for Bloggers and Cyber Dissidents, had been found on Mr Tinelli's computer, he added.

Mr Sommer also said that Mr Tinelli had "downplayed" his IT skills, yet he had been active in IT since his student days.

"It seems to me that one cannot be a successful publisher in new emerging electronic media without having a lively interest in the related emergent technologies," he added.

"He says he has no formal IT training but a great deal of practical knowledge and skill can be acquired simply 'on the job'."

Despite gaps in the electronic paper trail, Sir Martin's legal team believe they can tie Mr Benatti and Mr Tinelli to the creation and distribution of the blogs and emails.

Mr Benatti and Mr Tinelli deny any responsibility for the blogs and emails.

The case continues.

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