A tactical police commander has rejected suggestions he took "far too long" to enter the Lindt cafe after hostage Tori Johnson was shot dead.

The commander, known by the code name Delta Alpha, led one of the teams that entered the cafe on December 16, 2014. To enter the stronghold, he and his "Charlie" team had to cross a small foyer.

An inquest has heard that took between 19 and 21 seconds. A flash-bang distractor had failed to penetrate a glass door and detonated inside the foyer instead.

Michael O'Connell, SC, appearing for the family of killed hostage Katrina Dawson, asked for CCTV footage of the officers in the foyer to be played.

He suggested to Delta Alpha that 21 seconds was "far too long" to spend before crossing the threshold of the cafe.

"The delay that we have seen on that slow motion replay was unacceptable in those circumstances, do you disagree with that?" Mr O'Connell asked.

"In those circumstances, yes Your Honour," Delta Alpha replied to the coroner, maintaining his team could have done little differently.

Delta Alpha agreed that they had been expected to enter the cafe first, being closer to an easier entrance. But the Alpha team was first, coming through the main doorway.

Bullet fragments from one or two rounds fired by Alpha team struck and killed Ms Dawson, who had been lying on the ground behind the gunman, Man Haron Monis.

Mr O'Connell wondered whether that could have been avoided.

"What I'm suggesting to you is had Delta and Charlie [teams] been in there earlier that might have changed the outcome," he put to Delta Alpha.

But Coroner Michael Barnes said that was premised on a series of "mights".

Mr Barnes said it was "self-evident" that different actions on the night would have brought about different results. The question went unanswered.

Delta Alpha told the inquest on Monday that he had seen Monis directly behind a female hostage who was standing motionless. He said by the time he knelt to achieve a clear shot, Monis had been shot dead.

Mr O'Connell put it to Delta Alpha that he had in fact never seen Monis alive. Delta Alpha denied that. He said given the chance he would have shot Monis.

On Tuesday, still images from a three-dimensional reconstruction of the Lindt cafe were released, showing the lines of sight of snipers positioned in the Westpac, Channel Seven and Reserve Bank buildings.

The coloured sight lines, latticing the cafe, do not show what snipers could actually see during the siege.

Two snipers testified last week that although they had seen a figure who looked like Monis, they had lacked the legal justification to shoot him. Snipers must be satisfied their target poses an immediate threat of death or serious injury.

The inquest continues.