The leaders of Hewlett-Packard pleaded ignorance of the tactics used by private detectives hunting down the source of boardroom leaks, as the spying scandal claimed a fourth executive scalp at the computer manufacturer.
Mark Hurd, the chief executive, and Patricia Dunn, who was ousted as chairman last week, were grilled by a hostile Congressional committee, while Ann Baskins, who quit as Hewlett-Packard's general counsel yesterday morning, refused to answer questions.
Ms Dunn said private eyes who had been hired by Hewlett-Packard had obtained her own phone call lists, as they had more than a dozen other people. But both she and Mr Hurd said they had no idea about the tactics used, which involved impersonating the people involved so as to con phone companies into giving access to private records.
Wall Street has been mesmerised by the growing scandal at Hewlett-Packard, with its revelations of corporate skulduggery, including the spying on directors, the planting of monitoring software in journalists' e-mail and even a plan to infiltrate Silicon Valley newsrooms disguised as cleaners.
Ms Dunn said she was told that "checking telephone records was a standard investigative technique at HP and that they were drawn from public sources".
She told the hearing: "I am neither a lawyer nor an investigator and in this matter I relied on people in whom I had full confidence.... I would like to apologise that so many people were badly let down by this reliance."
Mr Hurd said he had received a report which might have alerted him to the tactics being used, but did not read it. "Not my finest hour," he said.
The House of Representatives' commerce committee had subpoenaed Ms Baskins and several of the private detectives who were believed to have been hired by Hewlett-Packard, but all pleaded the fifth amendment, refusing to answer questions for fear of incriminating themselves. The FBI and officials in the state of California are investigating whether HP's employees and contractors broke the law.
Congressmen ripped into HP over the tactics it used in the mole hunt. Tammy Baldwin said Hewlett-Packard had "led the nation on an expedition into corporate intrigue", and John Dingell said the investigation had proved a "fine case-study in deceit, dishonesty, improper behaviour and possibly illegal behaviour".
Several members expressed incredulity that Hewlett-Packard executives had not questioned the legality of their sources of information.Reuse content