Samantha Murphy: Top crime expert reveals major fear cops hold after breakthrough in search for missing Ballarat mother

A criminologist has revealed the mobile phone police found on the banks of a dam in their search for missing mum Samantha Murphy might be damaged beyond use. 

Ms Murphy vanished without a trace after she left her home on Eureka Street in Ballarat East, Victoria, on the morning of February 4. 

The 51-year-old left her home 18 minutes after sunrise, at 7am, for her 14km run through nearby Woowookrung Regional Park - a route she had done countless times.

In early March, almost five weeks after Ms Murphy's disappearance, local man Patrick Orren Stephenson, 22, was charged with her alleged murder. Her body has yet to be found. 

On Wednesday, police launched a new search in the hunt for her remains with the focus on a dam at a property south of Buninyong, approximately 14km from her home.

Officers located a mud-splattered mobile phone in a wallet at the water's edge, which was believed to have been found by a police tech detector dog.

In a statement issued shortly after the mobile phone was found, police said they had located some 'items of interest' during the search for the missing mum. 

University of Newcastle criminologist Xanthe Mallett told Sunrise on Thursday the discovery was 'very significant' as it could provide information on where Ms Murphy had been.

However, Dr Mallett added Ms Murphy's phone had been exposed to the elements for an extended period of time.

'Unfortunately, it may have been damaged,' she said. 

'Samantha Murphy has been missing for 116 days now, so almost four months.

'If it does transpire [the phone] is hers, they may not have got as much information as they could have done if it had been found earlier.

'It really depends on the quality of the phone and how damaged it is. Remember, it has been outside.'

Dr Mallett said technicians would immediately be assessing the condition of the phone and whether it belonged to Ms Murphy - but that process could take weeks.  

'They will be working on them quickly but it is not going to be short term. We are not talking days, we are talking weeks at the earliest,' she said. 

'Whether it has been for four months or if it transpires it is Samantha's or longer, we really don't know yet. We are going to have to wait and see exactly what condition that phone is in.'  

Aerial footage of the search showed detectives in jubilant celebrations after locating the phone at the water's edge of the dam. 

Police hugged, backslapped and shook hands in the wake of the discovery, in the video captured by the ABC. 

A team of police divers were also sent into the water to scour the small dam for any further possible evidence.

Dr Mallett said the reaction by police showed the discovery was a 'good moment' in their desperate search for Ms Murphy.

'I think we have to remember the police are people too,' Dr Mallett said. 

'This case has really touched everybody not only the Ballarat community but the wider community and the police. 

 'To find [her phone] after so long of no real leads... it would have been a really good moment for them, giving them hope they can progress this case for Samantha's family.'

More to come...