Top forensic psychologist reveals shock new Samantha Murphy phone theory - and why her alleged killer could be struggling in jail

A respected forensic psychologist has speculated that detectives who found Samantha Murphy's iPhone were 'tipped off' about its location.

Victoria Police last week discovered Ms Murphy's iPhone in the mud beside a dam on a property in Buninyong, about 19km from her Ballarat home.

The discovery comes four months after the mother-of-three vanished during a 14km run through the Woowookarung National Park on February 4.

Tim Watson-Munro said it was 'obvious' that detectives had been 'tipped off' about the phone's location and that he was surprised to hear it wasn't damaged.

'I wondered whether the phone had been there for four months,' Mr Watson-Munro told Daily Mail Australia on Thursday.

'I would have thought it was highly unusual to have a phone exposed to water without some natural degradation of the integrity and the hard-wiring of the phone after that period of time.

'So it may well have been that it was put there later, but that's purely speculative.'

Mr Watson-Munro said the phone may provide information about where Ms Murphy disappeared from and if she made any calls during the run.

'I saw the footage from when police discovered it and there were high fives and they were very, very happy about it,' he said.

'So they obviously see it as a positive development. The thing I find a bit intriguing is why the police chose that dam out of all the dams in the Ballarat district.

'They must have been acting on other information to go to that dam, but we don't know what it is and obviously they're not going to reveal that because the investigation is still in process.'

He said police would continue to hold their cards close to their chest.

'They're not going to telegraph all the information they have. No, they'll selectively release information,' the psychologist said.

'I'm sure they've got a bigger game plan in mind, which we're not privy to.'

Daily Mail Australia understands police are still searching for other key pieces of evidence, such as Ms Murphy's missing watch and headphones. 

In early March, almost five weeks after Ms Murphy's disappearance, local man Patrick Orren Stephenson, 22, was charged with her alleged murder. 

Stephenson is yet to enter a plea and will face court again in August. 

Mr Watson-Munro said first-time prisoners generally struggle behind bars and that those with high-profile cases can be targeted by other inmates. 

'In general terms, people don't cope well in jail,' he explained. 

'Jails are not holiday farms and it's like landing in a totally different world for a lot of these people, new rules being regimented, no decision making and so on.

'Again, in general principles, high profile individuals who go to jail can be targeted. They are perceived as individuals who may be vulnerable. 

'They can also be perceived as individuals who may have wealth in the community so they can be stood over for money. 

'And it's very hard for those sorts of people to blend into the general prison population.'