Hi JJ. It is not quite as simple as that. If HvB had premeditated this murder and searched for the axe murder on line he may well have done it on an unregistered phone. We don't know that yet. However, in the UK and South Africa it is still possible to pick up a free Pay As You Go (PAYG) SIM card without having to identify oneself and it is a doddle to buy over-the-counter minutes to use on it. One just needs to remember to use cash only. The use of the phone definitely would be picked up. If he was sensible he would only have used it to browse the internet when he was miles from home. Ownership of the phone would be unknown. This is a method commonly used by criminals and unless they do something stupid, such as use it at home or are found with it on their person, it is very difficult to prove it belongs to/is used by them. This is where his fingerprints would be very incriminating. He may have taken all these precautions but stupidly stored the phone at home but I suspect he will say the phone did not belong to him and was left by the intruder/s.
There are articles on the internet explaining exactly how to use a phone in this way.