Personally, I think a killer like the Beltway Sniper, with a little more care, probably could have gone on indefinitely. As I understand, the downfall was a combination of luck on the part of the investigators and sloppiness/bravado on the part of Muhammad and Malvo.
I live in Northern Virginia, and the situation was quite a bit more chaotic than it may have seemed to others outside the area. More often than not, people would crouch behind their vehicles while pumping gas. I’d see people run from their cars into the grocery store to minimize time outside. I knew people who would call the police every single time they saw anything they thought might be suspicious, which could be all sorts of ridiculous things. The shootings were seemingly more and more random, so it was just adding to the overall chaos. Hell, people were even straight up lying to the police about what they saw.
For instance, I remember one of the early tips was that they were probably in a white van. I didn’t quite expect the trunk thing, but I figured it wasn’t right at the time because, while it’s just too conspicuous and surprisingly common. Some people would freak out any time they saw one. Some people would even make up seeing stuff about how they saw the shooters get into or out of one, perhaps hoping for their 15-minutes. Cops were led on a wild goose chase by what was likely an honest, but incorrect, initial tip, followed by panicked citizens, and liars. Hell, I imagine Muhammad and Malvo, being aware of that tip and knowing it was bogus, took advantage of it in choosing some of their locations.
So, sure, we have better technology, but I’m not sure what more it could do to help with the investigation. If they were slick about picking fairly random targets over a large area, how coudl they possibly set up anything to give them extra information? People would have to be walking around with their cell phones with a customized app to really get much more info.
And with a little more planning, they could make it even more confusing. Have a team of more than the two people. Work together to split up the targets, but make effort to strongly connect them, like perhaps even using the same weapon and vehicle, so someone can be seen at work while a shooting happened far away, or give them time to make things seem more random, like have a shooting in DC, then one in Richmond just two or three hours later, so it could conceivably be the same person and look rushed but actually be well planned. Have someone on the team make a road trip to Cleveland or Atlanta or someplace like that and do one there, just to spread them thinner.
Still, in all of that, I imagine that they could cause even more widespread panic, as much because of the new technology, but ultimately, anyone would probably make a mistake that would get caught with enough people looking at it. I really don’t know what more they could do to get caught other than mostly getting lucky again.