A Sun reporter from south-east London paid a corrupt police officer to be his "stooge" amid a culture of "collective short-sightedness" at the newspaper, a court heard.
Vince Soodin, 39, is on trial at the Old Bailey accused of giving Sussex Police sergeant James Bowes £500 in exchange for story tips.
The court heard Bowes emailed The Sun about a three-year-old boy being bitten by a fox at a party in a school playground in Brighton on 19 June 2010.
He went on to give Soodin information about serial killer Peter Tobin the following month, jurors were told.
How the confidential material came into Soodin's hands only emerged in 2012 when the pieces of the "forensic jigsaw puzzle" were put together, connecting him with the officer, prosecutor Peter Wright QC said.
Wright said: "If the public cannot trust the policeman who can they trust? To whom do they turn, to whom do they confide, to whom do they rely on for protection, support and the maintenance of order in the public at large?"
He said the fact the information the journalist received was "relatively minor" was not a defence.
Nor was it any excuse that he acted within a culture of paying sources for confidential information at The Sun, jurors were told
Wright said: "There existed within certain quarters of The Sun a concerted collective myopia, a collective short sightedness, a culture of cultivating paid sources for confidential material.
"That it was sanctioned by others in the organisation, that it was considered fair game, that no one pointed out it was in fact a crime, is no excuse. It affords the journalist no defence."
He added: "Police sergeant Bowes was prepared to act as Vince Soodin's stooge in return for cash.
"It was in short therefore a corrupt arrangement in which, for what turned out to be just £500, Sgt Bowes and Vince Soodin were prepared between them to betray the public trust in the office of police sergeant.
"The offence is the corrupt agreement here. The fact it involved selling stories of relatively modest interest to the public, or of little to no interest beyond the back pages of the newspaper at that time, is not in any way a defence in this case."
Soodin, of Greenwich, denies the charge of conspiracy to commit misconduct in a public office.
Jurors were told Bowes, 31, was not in the dock because he had already pleaded guilty to misconduct in a public office.