The failure to approve, at any point during the 17-hour siege, a "deliberate action" plan – a surprise assault on the siege stronghold – occupied much of Commissioner Andrew Scipione's questioning on Wednesday.

The focus on the DA was a recurring issue at the inquest into the Martin Place siege.

Counsel assisting the coroner Jeremy Gormly, SC repeatedly asked Mr Scipione about a conversation he had with Assistant Commissioner Mark Jenkins on the night of the siege.

Mr Jenkins took over as a siege police commander at 10pm on December 15, 2014, as the crisis approached its final hours.

In a less than five-minute phone call between the two officers at 10.57pm, someone mentioned that a DA would be a last resort.

This is known because a police scribe made a log entry about the phone call, stating: "DA plan to occur as a last resort – COP".

"DA" was the kind of tactical assault police could launch to catch the offender off guard, while "COP" referred to "commissioner of police".

While conceding his memory of the exact words used in that conversation was not as sharp as it would have been right after the siege, he was certain he did not say the DA was a last resort.

"It is not an area I would have played a role," Mr Scipione told the NSW Coroner's Court.

"He [Mr Jenkins] has obviously come back and said in terms of the DA being a last resort. These were his words.

"They weren't my words."

Whatever was meant by the expression, Mr Gormly said, it was "striking" and "puzzling" that a DA was never approved by Mr Jenkins or the other police commanders throughout the siege.

That approval process came down to the police commanders who were in charge of operational moves that night.

Throughout his evidence Mr Scipione maintained he stayed out of operational decisions and recommendations at the siege.

Yet as the leader of the state's police force, conceded he wore the responsibility of the night.

"I wasn't responsible for decisions that were made but in terms of the buck, it stopped with me," he told the inquest.

The crisis ended after gunman Man Haron Monis shot dead hostage Tori Johnson, prompting police to carry out an "emergency action" – or "EA" – plan and bring the siege to an end.

Counsel for the Johnson family, Gabrielle Bashir, SC, said whether a DA would have made the circumstances worse or better held particular sensitivity for her clients, whose son was "executed by a terrorist" in Martin Place.

During his evidence earlier in the inquest, Mr Jenkins agreed with a suggestion that Mr Scipione mentioned the DA being a last resort.

He later changed his position and said it was likely he said it because he was on the phone and his scribe wouldn't have been able to hear what Mr Scipione was saying.

Mr Gormly suggested to Mr Scipione on Wednesday that there was at least a "meeting of minds" on the DA being used as a final option.

"If you're suggesting a meeting of minds indicates that as a result of that conversation or during that conversation I said to Mr Jenkins anything about or agreed with the notion of it being a last resort ... " Mr Scipione answered on Wednesday, "then there was no meeting of minds."

Before Mr Scipione gave evidence it was his deputy Catherine Burn's turn.

The two top cops were called to the inquest after a request from the families of the killed hostages and to ascertain if they had any role in operational decisions that night.

An email Mr Scipione sent off to Mr Jenkins and acting Deputy Commissioner Jeff Loy just before midnight could have been interpreted as a "direction", the inquest heard.

In it Mr Scipione referred to a hostage YouTube video and wrote: "Let's move to have it pulled down from You Tube as soon as possible."

He signed off with: "I'll leave it to you and others".

He disagreed with Mr Gormly's proposition that it was "as close as a direction as one could get".