Victoria Police could be prosecuted for its tardiness in handing over evidence about how they used information from 'Lawyer X' Nicola Gobbo against an ex-detective charged with murder.
Another 1000 documents are being reviewed that lawyers for the force believe might be relevant to a royal commission into police handling of informers, including Ms Gobbo.
Commissioner Margaret McMurdo on Tuesday said it was a case of "better late than never", after she ordered in January that the documents be handed over.
It is an offence not to comply and police could be charged, she added.
The documents relate to the police decision to deregister Ms Gobbo as an informer and use her as a witness against ex-detective Paul Dale.
In 2008, she recorded a conversation for police between herself and Mr Dale, who was charged with the murder of police informer Terry Hodson and his wife Christine.
Ms Gobbo was formally recruited by police as an informer from 2005 until 2009 when the decision was made to deregister her and use her as a witness.
In the recording, Mr Dale told her that underworld killer Carl Williams made a "very accurate" statement against him.
Mr Dale was charged after Williams claimed he was a go-between for the former officer and hitman Rodney Collins, who was also charged.
Charges against both men were dropped after Williams was murdered in prison in 2010.
"Carl's clear and made a very in-depth statement against me," Mr Dale told Ms Gobbo in a transcript shown to the commission on Tuesday.
When Ms Gobbo questioned its accuracy Mr Dale replied "very accurate".
"Very accurate to the point of every single time we met he seems to have documented it," Mr Dale said.
In his fourth day in the witness box Mr Dale took a stab at police, accusing handlers of leaving him sitting like a "dead duck" in recorded conversations with Ms Gobbo, who he said was his lawyer.
"Nicola Gobbo wore a wire when I was seeking her out for legal advice - if that's not using her against me, I don't know what is," he said.
Geoff Chettle, who is representing a number of former Source Development Unit handlers, challenged Mr Dale's claims but the latter didn't back down.
He said he had been approached by one of Mr Chettle's clients "who totally disagrees with what your SDU members did".
That man is due to be called as a witness.
Australian Associated Press