Weren't their cybersecurity knowledge (or lack thereof) as catastrophical as it was (as is not surprising by teens), they likely wouldn't venture into that. The police got them by their fb conversations they did not delete. One of the boys even had the luck to take the hold of the rapist's phone and get into it, and drained his bank account by sending the money to his own. Here I suppose they either tortured him for the PIN, or the man had it written somewhere visible. Police even found some of the man's things at the boys' home. They did not switch off their own phones, also likely did not check for cameras in the car, and if the oldest guy drove them there with his car, it was likely recorded by all the speed cameras on the way.
And even if they done right hiding all the other traces (no), with that many people involved it's very likely at least one of them would brag about it at some point to their friends....Wait, check, they actually did.
Some good news tho: ''Prosecutors said his death would likely have caused severe suffering.''