Court hears operator of jumping castle in Hillcrest School tragedy ‘not competent’ to make safety assessments

Roderick McDonald, a mechanical engineer giving evidence in the trial of operator of the jumping castle at the centre of the Hillcrest Primary School tragedy of 2021, has advised that the accused "should have sought help" in understanding her obligations and the safety standards in operating the inflatable.

Inflatables expert McDonald has been giving evidence the Devonport Magistrates Court this week on the 2021 jumping castle tragedy at Hillcrest Primary School, which caused the deaths of six children

The criminal proceedings against Rosemary Gamble, operator of the Taz-Zorb jumping castle at the centre of tragedy has seen her accused of failing in several ways, including in the use of four pegs/start pickets to anchor the castle, which had eight anchor points.

Gamble’s business, Taz-Zorb, provided the zorb balls and jumping castle to Hillcrest Primary School for its end of year 'Big Day In' celebrations on 16th December 2021, which ended in tragedy.

She has pleaded not guilty to failing in her work health and safety obligations.

Giving evidence McDonald said if all the star pickets that were available on the day were used, the jumping castle would have stayed on the ground during the wind event.

Defence lawyer Chris Dockray has argued there was nothing Gamble could have done on the day to prevent the tragedy that unfolded.

However, McDonald told the Court that if star pickets that were available to Taz-Zorb on the day they were used, the jumping castle would have stayed on the ground during the wind event.

He stated "if all eight star pickets were used it would have endured the event”, adding that if eight 30cm ‘J-shaped’ pegs were used to anchor the castle, it would have had the potential to withstand the event.

Dockray has told the court that Gamble only received four of these pegs when she purchased the jumping castle from East Inflatables in 2015, and that she sought assurances from the company that their products complied with Australian standards.

In cross examination of McDonald, Dockray suggested that his client's non-compliance with relevant Australian standards followed directly from East Inflatables' own non-compliance.

The lawyer led McDonald through pages of details about the standards as they applied to the manufacturer, highlighting several areas and asking if the company was non-compliant, which the engineer said they were.

At one point Dockray described the company's non-compliance as "gross and significant", which McDonald agreed to.

Dockray suggested “if she hadn't been provided the information how could she know what she didn't know?"

However, McDonald said there were several organisations that WorkSafe could have put Gamble in contact with.

He noted "I can't comment on Ms Gamble's thinking or the quality of the research she's done.”

Earlier, McDonald told the Court that to ensure safety operators of devices like jumping castles should be either following manufacturer's instructions "to the letter" or engaging an engineer to develop a safe operating procedure.

Robert Monte, Gamble's partner who also helped with Taz-Zorb, said she had never engaged an engineer.

McDonald said a national association of engineers that he chaired had about 26,000 members who would be able to complete such an inspection.

The Court has previously heard the jumping castle itself was purchased for about $3,500 from Chinese manufacturer East Inflatables in 2015.

McDonald said Taz-Zorb was inconsistent in their operation of the jumping castle, and that Gamble was not competent to make the necessary safety assessments or deviations from the manufacturer's instructions.

On several occasions McDonald described Taz-Zorb's approach as inconsistent, and again on Tuesday morning compared the need for consistency in jumping castle operation to road safety, commenting “it's like deciding the traffic's light and not putting on your seatbelt.”

Tragedy may still have occurred with all eight tethers
In his earlier opening statement to the Court, Dockray said his client could not have done anything on the day to prevent the tragedy because "it was not possible to anticipate or predict the emergence of the dust devil".

He suggested that because of that, and because it was not possible to calculate the dust devil's exact forces and windspeeds, it was possible that even if eight pegs that met Australian standards were used to anchor the jumping castle, the anchorage system may have failed.

Mcdonald replied that this was “possible”, prompting Crown Prosecutor Madeleine Wilson SC to seek clarification of the response.

McDonald said that the possibility of the failure Dockray referred to was dependent on several other variables and failures, most of which could not be predicted.

Black Swan Event
The Crown case closed on Wednesday morning, and defence began calling witnesses, including their expert Dr David Eager, Professor of Risk Management and Injury Prevention at University of Technology Sydney (UTS).

In his report, Dr Eager, a longtime Chair of Standards Australia Committee ME/51, Amusement Rides and Devices responsible for a range of standards including AS 3533.1-1997 Amusement rides and devices, said the wind conditions when the jumping castle was flung around 10 metres in the air were “statistically rare” and described the incident as a “black swan event”.

He advised “it was concluded that the jumping castle anchor system catastrophically failed as a direct result of the wind event” adding that “it was concluded that, more likely than not, that the anchor system would have failed even if eight ground anchors would have been installed.”

Dr Eager told the court that he believes it would have been a fair assumption on Gamble’s not to buy more than the four pegs provided to her when East Inflatables sent her the jumping castle.

Dr Eager believed that Gamble and the Taz-Zorb workers were experienced in operating and setting up inflatable devices, adding “in my eyes, they are competent because they had done it 100 times.

“It’s not rocket science putting one of these things up. You don’t need a PhD to plug it in and pump it.”

Prosecutor Madeleine Wilson took issue with some of the terminology used in Dr Eager’s report, which was tendered as evidence, and is seeking to have certain parts of it removed.

Magistrate Robert Webster will decide whether to remove those parts when the hearing resumes before Dr Eager takes the witness stand.

The Court is expected to finish hearing evidence as of tomorrow.

Editor’s note: A ‘black swan’ event is a high-impact event that is difficult to predict under normal circumstances but that in retrospect appears to have been inevitable.

Image: A jumping castle understood to be similar to the one at the centre of the Hillcrest Primary School tragedy. Credit: Taz-Zorb website.