Top cops delayed at Lindt inquest

The long-awaited evidence of NSW's three most senior police officers at a coronial inquest into the Sydney siege has been delayed by several weeks after hitting a surprise snag.

Acting Deputy Commissioner Jeff Loy arrived at the inquest on Tuesday morning but never made it into the witness box, where Deputy Commissioner Cath Burn was due to give evidence afterwards.

Commissioner Andrew Scipione was expected to appear on Wednesday afternoon.

But counsel assisting the coroner, Jeremy Gormly SC, said a bundle of documents provided by the NSW Police Force in relation to the top ranking officers had not yet been properly vetted.

The documents were offered up in June after families of slain hostages Katrina Dawson and Tori Johnson requested that the three senior officers be called to give evidence.

Included in the bundle were cabinet documents to be covered by NSW parliamentary privilege, emails and text messages, Mr Gormly told the inquest.

He said while the documents were handed over in June, he had waited until receiving statements from all three officers to go through them, and had ultimately overlooked them.

Mr Gormly accepted full responsibility and said he had personally apologised to the families of Mr Johnson and Ms Dawson for the delay.

He said the documents still needed to pass through administrative hurdles and be provided to various legal parties.

"These witnesses are just too important to deal with in any other way other than properly," Mr Gormly told the inquest.

"The fault for this problem is mine. It's not the fault of any other person or party.

"It is obviously really regrettable and I apologise in particular to the families."

Lawyers for the families of the two slain hostages did not object to the delay, telling the inquest they were grateful to be given time to carefully consider the documents rather than having to cross-examine "on the run".

NSW Coroner Michael Barnes said it was appropriate to postpone the hearing to give the parties the opportunity to view the documents.

Mr Barnes wants to examine whether any of the officers inappropriately interfered - or failed to intervene when they should have - during the deadly December 2014 stand-off.

All of the officers have denied playing key operational roles during the siege.

The inquest has been adjourned until August 15.