Patricia Dunn, the former chairman of Hewlett-Packard, and three others involved in the computer company’s boardroom spying scandal were effectively let off last night after reaching a plea deal in California.

Ms Dunn, forced to leave HP because of her central role in the spying plot, declined to enter a plea when faced last night with a misdemeanour charge of fraudulent wire communications after which the court dismissed her case.

Meanwhile, Kevin Hunsaker, the former head of corporate ethics at HP, Ronald DeLia and Matthew DePante, both private investigators, pleaded no contest to the same charge.

The court did not accept their pleas but offered to dismiss the case against the three men if they completed 96 hours of community service before September 12.

Ms Dunn avoided a similar punishment because she is a cancer patient.

The three men also face the prospect of paying restitution, although no injured parties or victims of the crime have come forward, meaning that a fine is unlikely.

Once the terms of the plea deal are met, none of the defendants will have a criminal record and will be free to take up directorships.

A source close to the case told The Times that the misdemeanour charges were “only slightly more significant than a parking ticket” and were reached after hours of closed-door meetings between prosecutors, lawyers and the court.

The guilty charges bring to a close the six-month investigation by the California attorney-general into boardroom spying at Hewlett-Packard.

The case centred on an illegal practice known as pretexting that involves obtaining by deception personal details such as phone and e-mail records.

The company hired private investigators to find out who was telling the media about secret board meetings after it ousted Carly Fiorina as chief executive in 2005.

HP decided that George Keyworth, a long-term director, was doing the leaking.

When Mr Keyworth was accused at a board meeting on May 18 he refused to resign but Thomas Perkins, another director, quit in protest, prompting the California investigation.

Pretexting exists in a legal grey area in the US, but the HP case has helped to expose its illegality in the state of California.

“The outcome of this case validates the attorney-general’s view that pretexting, more simply put as lying to get the personal information of others, is illegal,” a spokesman for the California attorney-general’s office said.

Business big shot

Patricia Dunn is a fighter. Last night she emerged the victor in the most high-profile battle of her career as a court in California dismissed the case against her in the spying scandal.

Although forced to resign from Hewlett-Packard, Ms Dunn, 52, is still regarded as one of the most influential women in America.

She was born in Las Vegas to a showgirl mother, who died at an early age, and a Vaudevillian father, who raised his daughter alone.

She attempted to pursue a career in journalism, but was put off by the poor financial prospects of a life in print.

Instead, in 1978, she joined Wells Fargo Investment Advisors as a secretary.

Soon after Wells Fargo was acquired by Barclays Global Investors, the UK asset manager, in 1995 she was appointed chairman and chief executive — not bad for a girl from the typing pool.

In 1998 she was appointed director of HP and was listed as one of the most powerful women in America by Forbes only two years later.

She rose to the chairman’s seat after Carly Fiorina was ousted in February 2005.

Her battles have not always played out in the boardroom, however. In 1998 her doctors diagnosed breast cancer and melanoma. More recently, she was found to have ovarian cancer.

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