Theo Hayez inquest: Phone data placed phone on hills below Cape Byron

Evidence of a telecommunications specialist appears to have supported a police theory about Belgian backpacker Theo Hayez’ movements after he disappeared in Byron Bay.

Evidence of a telecommunications specialist appears to have supported a police theory of Theo Hayez’ movements in the hours after he was last seen in Byron Bay in 2019.

The inquest into the 18-year-old Belgian backpacker’s disappearance began in Byron Bay late last year and has continued this week.

Theo was last seen leaving Cheeky Monkey’s nightclub on Jonson Street in Byron Bay about 11pm on May 31, 2019.

Professor Aruna Seneviratne, a telecommunications expert from the University of NSW, was among the witnesses to address the inquest in late 2021.

Much of his evidence was heard in closed court at the time.

Professor Seneviratne appeared before the inquest again on Thursday.

Counsel assisting the coroner, Kirsten Edwards, said the professor had “some new information of some significance”.

“It may be that we have been able to further refine where Theo’s phone might have been located at around 1am or before that period of five hours where the phone stops communication with the towers, before coming back just after 6.15am, albeit very briefly,” Ms Edwards said.

Professor Aruna Seneviratne (right) has given evidence focusing on telecommunications before the inquest into the disappearance of Theo Hayez in Byron Bay. Picture: Liana Boss

Professor Seneviratne was taken to Cheeky Monkey’s, the northern end of the cricket nets, the start of the Milne Track on Milne Street – which heads into bushland toward Tallow Beach – and other areas of interest including local telephone towers.

He gave evidence that Theo’s phone connected with a tower on Massinger Street and the more distant Ballina reservoir tower almost simultaneously and a number of times in the early hours of June 1, 2019.

Coverage arcs suggest Theo’s phone was 1.795km from the Massinger Street Tower and 24.9km from the Ballina tower when it connected with them.

Using a form of triangulation, Professor Seneviratne placed Theo’s phone in an area of bushland above Tallow Beach – toward Cape Byron – between midnight and 1am.

“It is not a precise science by any means, but there are certain constraints that you can put on it,” Professor Seneviratne said.

“For example, it cannot be in the blue area; blue represents water.

“A phone will not survive in salty water.”

The inquest heard he had “very high confidence” phone data was consistent with Theo moving away from the Massinger Street tower between about midnight and 1am.

When asked whether this meant phone data was consistent with the police theory that Theo, or at least his phone, was moving away from the beach and up the headland toward the lighthouse, Professor Seneviratne stopped short of completely confirming that trajectory.

But he noted there terrain limitations that limited realistic paths of movement.

The view from near the Massinger Street phone tower in Byron Bay, looking toward Cape Byron and the area where phone data has placed Theo Hayez’ phone in the early hours of June 1, 2019. Picture: Liana Boss

Professor Seneviratne told the inquest his opinion was that GPS location data showed a reliable location for Theo’s phone up to 12.05am on June 1.

He confirmed GPS data stopped being recorded 12.05am until 1.02am.

But Telstra network data was recorded from during that time.

Professor Seneviratne said Theo’s phone was in an area of “very poor” reception during that period.

For the following period to 6.17am, Theo’s phone didn’t connect with any tower, the inquest heard.

Theo’s phone reconnected to the Telstra network from 6.17am until 1.47pm.

After 6.17am, it had an even poorer signal, he said.

The professor ended his evidence with a message for Theo’s family.

“I just want to say that what I tried to do is look at it from a scientific point of view and I’m really sorry for the pain that you have gone through,” he said.

“I’m just trying to help.”

The inquest continues.