Three senior journalists at the defunct News of the World tabloid have already pleaded guilty to hacking phones, a prosecutor revealed Wednesday, calling it a sign of the scope of the illegal behavior at the Rupert Murdoch-owned publication.
Prosecutor Andrew Edis said ex-news editor Greg Miskiw, ex-chief reporter Neville Thurlbeck and former reporter James Weatherup all entered guilty pleas ahead of this week's high-profile phone hacking trial of former News of the World editors Rebekah Brooks and Andy Coulson, who are in the dock along with Brooks' husband Charles and several others.
Private investigator Glenn Mulcaire, who had already been convicted of similar offenses back in 2007, also pleaded guilty.
Brooks and Coulson, both 45, deny a variety of phone hacking-related charges.
(Read more: Ex-Mudoch editor Brooks denies hacking charges)
Speaking during the trial's opening arguments, Edis said that the guilty pleas show "there was a conspiracy which involved a significant number of people."
Edis said Brooks and Coulson must have known about phone hacking by staff under them because "they controlled the purse-strings" and signed off on illicit payments.
Coulson is accused of conspiring to hack phones and make illegal payments to a police officer for a notebook containing contact details of members of the royal household, while Brooks is alleged to have paid public officials including a member of the armed forces and a senior defense official for information while she was editor of The Sun.
"Mrs. Brooks personally approved nearly 40,000 pounds for stories" to the defense official, Edis said.
The hacking case -- which is not expected to end until well into next year -- is the first big criminal trial spawned by the 2011 revelation that the News of the World had hacked the mobile phone voicemails of kidnapped 13-year-old Milly Dowler, who was later found murdered. Brooks edited both the News of the World and its sister paper, The Sun, and was chief executive of Murdoch's British newspaper division. Coulson also edited the News of the World before becoming communications chief to Prime Minister David Cameron.
(Read more: Ex-News Corp execs hauled to trial in hacking case)
The hacking scandal first exploded in 2006 following revelations that the News of the World eavesdropped on members of the royal household. But it resurfaced in 2011 following the Dowler revelations, leading to dozens of arrests and resignations. The renewed scandal rocked the British establishment and led Murdoch to shut the 168-year-old newspaper.
Photographers have clustered outside the court, known as the Old Bailey, since the trial began on Monday. More than 60 journalists are covering proceedings from the courtroom and an overspill annex.
Edis urged jurors to put aside the copious pre-trial publicity surrounding the case, saying Wednesday that the issue they had to consider was a simple one.
"There was phone hacking," he said. "Who knew?"
--By The Associated Press