Have any ideas?
. . .and the 'code'? (Yes, it is possible to figure it out. . .just not likely in this scenario) . . .
that said. . .my first thought was a 'set up'. .
By the same token, however. . . it is possible that to make this killing look like someone else did it. . .they decided they had no choice but to get really ugly. . .
Lie dectector tests? They can explain how it is; they were using bank card post killings? They have alibis? (Forensic info not mentioned?)
Wouldn't be too difficult to leave it "lying around" somewhere where they might pick it up. For instance, how long after the death of the family was it until the card was first used?
It's quite common for petty (and not so petty) criminals to stumble across the scene of someone else's crime and dip into the cookie jar so to speak. And, by all accounts, neither of the two "suspects" is going carry off the prize for being the sharpest knife in the drawer.
These two are going to get well and truly stitched up. A political decision has already been reached that Islam could have played no part in the murders.