The case against former News of the World editor Andy Coulson was neither "rigorous, open-minded or fair", the hacking trial heard.
A number of "gaps in the evidence" in the prosecution against Coulson were highlighted by his lawyer in his closing speech at the Old Bailey.
Among them was the failure by police to fingerprint members of the royal household to check if one of their number, and not unidentified police officers, was the source of royal directories sold to the NotW, jurors were told.
The prosecution also kept evidence of the extent of former royal editor Clive Goodman's phone hacking from the jury, leaving it to the defence to expose it for the first time, the court heard.
Coulson, 46, is on trial accused of conspiring to hack phones and conspiring to commit misconduct in a public office by agreeing with Goodman to pay for two royal phone books.
His lawyer Timothy Langdale QC told jurors: "Operation Weeting commenced in January 2011 as a high profile investigation and attracting a high degree of public interest and media scrutiny. It must have been important that it would be a rigorous investigation.
"We suggest as far as Mr Coulson is concerned it has been none of those things - rigorous, open-minded or fair.
"Case theories have changed at a moment's notice once they have been exposed as impossible.
"Criticisms of the police investigation have been brushed aside for blame to be cast elsewhere, often in News International's direction.
"It's almost as if the juggernaut must keep moving."
Mr Langdale told jurors that it was their responsibility to "do what the investigation so often failed to do - which is scrutinise, analyse, and come to a fair conclusion".
The lawyer gave four examples of what he asserted were failures in the investigation.
He said no-one checked details of reporter Dan Evans's evidence that he had hacked actor Daniel Craig's phone and played a message from Sienna Miller to Coulson at a time the editor was at the Labour Party conference in Brighton.
And while the prosecution relied on emails from Goodman as evidence of Coulson's involvement in hacking, it kept from the jury extent of the royal editor's hacking, the court heard.
Mr Langdale said: "For some reason the prosecution decided not to put that evidence before you."
He went on to question email evidence of Coulson ordering to "do his phone".
"How was it that at the beginning of this trial the prosecution told you 'do his phone' meant hack Calum Best when there was no evidence at all Calum was hacked either before of after that communication?" he asked.
And on the charge that Coulson conspired to pay a public official for royal phone books, he said: "The failure to fingerprint members of the royal household as to who it was may have been the source of those directories - you obviously must consider these matters."
Coulson, 46, of Charing, Kent, along with six co-defendants denies the charges against him.
Mr Langdale asked: "If it is the prosecution case the phone hacking was an open secret at the NotW, why are there no emails requesting hacking or sanctioning hacking?
"Attempts by the prosecution to try and find them produces one - the 'do his phone' email - demonstrably, we suggest, a misconception. The prosecution case is this is a direct instruction to hack in black and white. If it was an open secret and everyone knew, why are there not more?"
He continued: "Lastly this: where is the office cat?
"That apparition, the office cat, has been seized upon by the prosecution, having been used by that thoroughly unreliable witness Dan Evans and picked up by that thoroughly unreliable witness Clive Goodman.
"A notable feature of this case is that the prosecution failed to call before you a single witness to testify that Andy Coulson was involved in phone hacking at the NotW who does not have an agenda of their own to pursue."