There’s nothing groundbreaking here; it’s casting a wide net with cell phone geolocation data and then winnowing it down using other evidence and investigative techniques. And right now, those are expensive and time consuming, so only used in major crimes like murder (or, in this case, murders).

What’s interesting to think about is what happens when this kind of thing becomes cheap and easy: when it can all be done through easily accessible databases, or even when an AI can do the sorting and make the inferences automatically. Cheaper digital forensics means more digital forensics, and we’ll start seeing this kind of thing for even routine crimes. That’s going to change things.