I don't understand why the police are not arresting Borce for the murder of Karen. It is obvious they have enough information for a conviction. I am puzzled. I can think of two options:
1) they don't want to arrest him and then still look for her body afterwards. But i don't see why that is a drawback to an arrest now, while the search for her body is ongoing. Or,
2) they suspect someone else is involved and need more time to precisely locate who did the disposing- Borce or VR. If they go to trial now and allege that Borce disposed of his wife, but it turns out in 3 months time after some CCTV footage arises of VR driving up that way, then they'll look like fools having charged Borce with the murder and disposal, though having to then change the charge sheet to accomodate VR for the disposal.
Something like this must be in play, as it makes no sense to have Borce caught practically red handed though not having him arrested. Why? Shouldn't they be arresting him now, busting his balls, in order to find a torso which might preserve some evidence? It seems fishy to me.