A 21-year-old student has pleaded not guilty to charges of hacking into the personal e-mail account of Sarah Palin, the Alaska governor and former Republican vice-presidential nominee.

David Kernell, a University of Tennessee student, faces four charges after allegedly using publicly available information about Mrs Palin to guess the password to her Yahoo! e-mail account while she was on the campaign trail last September.

Kernell, the son of a Democratic Tennessee legislator, is accused of correctly answering a series of personal security questions to reset the password. He is said to have read the e-mails, made screenshots and posted his exploits on the web using the nickname "rubico."

The indictment said that at least one other person followed a similar path into Mrs Palin's account. Some material from the e-mail account was posted on the Wikileaks website.

Three new counts were added to the original charge of intentionally accessing the account without authorisation when the student appeared before a US district judge in Knoxville, Tennessee. Kernell now faces charges of fraud, unlawful electronic transmission of material outside Tennessee and attempts to conceal records to impede an FBI investigation.

If convicted, he faces a maximum punishment of 20 years in prison, a $250,000 (£180,000) fine and five years of supervised release, according to WBIR-TV in its report of the hearing.

Judge Clifford Shirley told Kernell that he was free until trial, set for October, as long as he met certain conditions, including using a computer only for class work.

Kernell is the son of longtime state Representative Mike Kernell of Memphis, chairman of Tennessee's House Government Operations Committee.

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