Any Facebook posts, videos, photos and text messages deleted by the Roast Busters group would not stay hidden from the prying eyes of police for long, a private investigator says.

Daniel Toresen, director of private investigation firm Thompson and Toresen, said a large proportion of digital media including text messages, photos and videos could be recovered from smartphones and computers.

Facebook posts, including videos and photos uploaded to the site could be viewed through internet caches - saved snapshots of websites - he said.

Police could use search warrants to get the information directly from Facebook, Mr Toresen said.

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"In terms of the [alleged] offenders' computers, yes there will be cache information on the actual machine, so when you upload a video, or photo from your computer up to wherever, there is a trail of that process."

Deleted media from seized smartphones could be recovered depending on the type of phone, Mr Toresen said.

"For instance iPhones - we can clone an iPhone 4S then get back [deleted information]," he said.

"It really depends on the phone because a Nokia for instance - if you delete it on a Nokia - you can't get it back. The phone is not storing the same amount of data and information in the same way as an iPhone."

All information from laptops could be recovered, he said.

Mr Toreson said police would clone every single electronic device they seized.

"They're fully staffed with all the best equipment money can buy in terms of forensics."