William Tyrrell has been missing since 2014. Photo / File
William Tyrrell has been missing since 2014. Photo / File
Even if the revamped efforts to find traces of William Tyrrell prove fruitful, it is highly unlikely police will uncover what actually happened to him when he vanished in September 2014.
Cases that remain open for such a significant period of time almost never result in concrete answers being uncovered, crime scene reconstruction expert Scott Roder told news.com.au.
Even if investigators found half of William's remains, the odds were stacked against them determining when and how he was killed, said Roder, who hosts the Crime Scene Time Machine podcast.
"Even if they find the bones, and identify them as this child, there's a very low percentage chance of them being able to determine his manner of death.
"They're certainly not at this point in time going to be able to do any sort of toxicology or skin tissue exam or anything like that. There's going to be no trace evidence."
The mystery could remain unsolved forever, unless of course there was something on the remains that pointed to a specific cause of death, Roder said.
"Unless there's something on the bones that is found that can be interpreted as a specific cause of death, the chance of being able to determine the manner of death, or even compile evidence, is pretty slim."
He said even finding remains and identifying them as William's "would be a big success at this point in time".
"Trying to find physical evidence after seven years is very hard."
Glaring issue with finding remains
Detectives sifting through tonnes of soil pulled from the Kendall property of William's foster grandmother had a mammoth challenge on their hands given how minuscule his remains were likely to be, Roder said.
Strike Force Rosann dig through an area of bush near the foster grandmother's house. Photo / NCA NewsWire/Peter Lorimer
"If you took a marble and broke that into seven pieces, you could be looking for something that small."
Given William was just 3 when he went missing, his skull at the time was still in four pieces and relatively "flexible and pliable", meaning they would have more easily detached and spread.
The chin bone and the hip and femur bones might be slightly easier to locate, he said.
Forensic experts, archaeologists and forensic anthropologists have advised officers to dig to a depth of about 15cm in their search of areas surrounding the Benaroon Drive home.
So far police have searched less than 20 per cent of the 1.5sq km area, with about 15 tonnes of soil having been moved to a clandestine lab.
Roder argued that if William was buried somewhere around the property, his remains would be relatively close to the surface given the prominence of tree roots in the area.
"Because it's dense bushland, you can't really dig too deep because of all the roots," he said.
"Maybe there's evidence that he was dragged off into that bushland."
He added detectives were likely looking into the possibility local wildlife had played a role in moving parts of William's remains across the area being searched.
Potential evidence removed from search area
A forensic officer from NSW Police was pictured on Tuesday carrying a bag understood to contain material from the eastern side of Batar Road, less than 900 metres from the boy's foster grandmother's home.
Strike Force Rosann detectives returned to area last week after "new and fresh leads" came to light, with their renewed search efforts expected to last up to three weeks.
The search was initially focused on the home where William was last seen on September 14, 2014, with officers digging through the garden bed below its second storey balcony.
Officers this week appear to be focusing on an area of bushland along Batar Creek Road, less than a kilometre from the home.
