Indeed. Sorry to beat a dead horse, here, but all the scenarios that have AK and RS coming on the crime scene after the fact and then deciding to stage a cover up make no sense to me at this point.
Immediately after the murders, when both AK and RS did in fact make false statements to police, I could have entertained the notion that they did nothing but the cover up. But by the time they got to trial, their lawyers would have had to know they were better off confessing to tampering with evidence (the Italian equivalent, of course) than risking a conviction for murder.