Barnes described the unnamed consultant psychiatrist’s role advising police on tactics during the December 2014 siege as “suboptimal”.

He also found that tactical police waited “10 minutes” too long to storm the Lindt Cafe after Monis fired his first shot.

“He (the psychiatrist) made erroneous and unrealistic assessments of what was occurring in the stronghold,” Barnes said as he handed down his findings from the inquest into the siege on Wednesday.

“He gave ambiguous advice. And he was permitted to go beyond his area of expertise to give advice about Islamic terrorism,”

Barnes said the inadequate advice from the psychiatrist was partly to blame for how police commanders “underestimated the threat Monis posed”.

“This was partly because they were not given a complete and balanced nature of the available intelligence; partly because they placed undue reliance on the consultant psychiatrist; and partly because they did not adequately challenge or test information and advice they received about the mood in the cafe, the likelihood that Monis might harm the hostages,” Barnes said.

“While this is obvious in hindsight, with more rigorous and cautious analysis it could also have been discerned at the time.”

Barnes called on the NSW Police to consider expanding the number of psychological advisers it uses as consultants and introduce clear policies for any that are called on to assist in future.

Having a diverse panel of experts available would help reduce the chances of any single psychological adviser going outside their area of expertise, he said, and provide siege responders access to more reliable information.

Police stormed the Martin Place cafe in the early hours of December 16, 2014 after Monis shot dead hostage Tory Johnson 17 hours into the siege.

Monis, 50, was shot dead by police and hostage Katrina Dawson was fatally wounded by at least seven police bullet fragments.

Barnes also called on NSW Police to review the training and accreditation of police negotiators and the means by which they are assessed, saying the “contain and negotiate strategy” adopted during the siege had been a failure.

While such a strategy had been appropriate early on and even after the incident was assessed to be a terrorist event, there was no evidence that police made any evaluation of whether it remained appropriate as the siege dragged on.

A reassessment should have led to changes to the approach of negotiations with Monis while alternative measures for resolving the siege were considered, Barnes said.

“The negotiators failed to undertake and structured assessment of whether headway was being achieved. They had no procedure for undertaking such assessment,” he said.

Barnes said Man Monis “maliciously” executed Johnson, while Dawson was killed by fragments from police bullets, in what Barnes said was “a terrible accident”.

The coroner said an emergency action “should have been initiated” by tactical police following the first shot of Monis at 2.03am on December 16.

“The 10 minutes that lapsed without decisive action by police was too long,” Mr Barnes said.

“Tori Johnson was executed in the meantime before the decision to enter the cafe was made.”

He said the first shot “made it clear there was little to no chance of resolving the siege”.

New NSW police commissioner Nick Fuller has conceded armed officers should have been sent in earlier to rescue the hostages.

“In hindsight, as with everything, we know we should have gone in earlier,” he’s told ABC TV’s Four Corners program to air next week.

“It does not guarantee there will not be a loss of life … but clearly a deliberate action is a much more professional action and a lower risk in terms of emergency action.”

The families of Lindt Cafe siege victims, Katrina Dawson and Tori Johnson, were at the court today to hear the findings.

– AAP