NSW Police Deputy Commissioner Catherine Burn gives evidence at Sydney siege inquest

NSW Police Deputy Commissioner Cath Burn has taken the stand at a coronial inquest into the deadly Sydney Lindt cafe siege.

Ms Burn, the state's head of counter-terrorism, has entered the witness box to give her highly-anticipated evidence after Acting Deputy Commissioner Jeff Loy fronted the inquest earlier on Monday.

The two senior officers, along with Commissioner Andrew Scipione, have denied playing key operational roles during the December 2014 siege.

NSW Coroner Michael Barnes is now seeking to determine whether any of the police chiefs inappropriately interfered in the Martin Place stand-off or failed to intervene when they ought to have.

Ms Burn reiterated her position that she played no operational role during the siege soon after she took the stand on Monday afternoon.

She said there was "a very real need" for executive officers to leave such matters to police in operational posts, adding such an intervention may even prove dangerous.

Ms Burn also denied offering any suggestions to Commander Mark Jenkins when the pair discussed progress in negotiations shortly before 11pm on the night of the siege.

"Whether I had the right (to make such suggestions) it's not something I would have thought appropriate," she told the inquest.

Ms Burn was also pressed about text messages she sent during and soon after the siege which were deleted and have not been recovered.

Many of the texts related to setting up briefings or meetings, while others were received from members of the public wanting to pass on their support, she said.

Ms Burn said other than a text message to Mr Loy soon after the siege had ended, asking for a debrief on the execution of an "emergency action" (EA) which saw police storm the building, she couldn't recall any others which pertained to an EA.

It was also "highly unlikely" any of the deleted text messages related to progress in negotiations, she said.

"To my knowledge and recollection none of the texts I had were texts I thought I needed to keep, that I needed to retain," Ms Burn said.