I decided that I can't stay away. But instead of debating I'll just contribute where I can. This is all MOO.
I agree with everything but the GPS data being a hindrance for trial. The cell tower data is much much stronger than lack of GPS data is.
For one, the only reliable place to retrieve historical GPS data in a Android device is the Google Maps Timeline feature. As it comes installed and turned on by default on the majority of Android devices. If BK had the Timeline feature turned off (as many privacy focused people do) or uninstalled Google Maps before the crimes LE not finding GPS data would not be very surprising. As the only other way to have GPS data in there would be to Ask an App like Waze for Directions to the Crime Scene. I could be wrong but I don't think Android's default settings allows any other apps to passively collect location data. But if I am wrong then this makes BKs predicament only worse.
We also know (via the video from the Indiana stops) that his Elantra was equipped with the base infotainment system option that contains absolutely no GPS hardware whatsoever.
Secondly, GPS data is extremely easy to spoof on Android devices. Either on the device via easily accessible apps (you can literally download them in a minute or two) or via a desktop emulator. You could essentially create an entire trail of breadcrumbs. Though most of the uses I've seen have nothing to do with quadruple murders.....cheating on Pokemon Go, cheating on a spouse, making Netflix think you totally should have access to that spanish novella.
Cell towers on the other hand are pretty much IMPOSSIBLE to lie to. This is by design. They to rely on a few things. I'll talk about two of them. Unlike GPS....IMEI which is unique to each and every cellular device is extremely hard to spoof. And the fact that spoofing those identifiers will get you thrown in jail (read: illegal) makes it a lot more difficult to find apps or anyone openly creating tools to do it. IMEI (and the other standard I'm going to mention) have been designed with global crime fighting in mind.
Let's say that you managed to successfully spoof IMEI. It would essentially be a gigantic waste of time because the IMSI encrypted on your SIM card is going to get you caught. And the encryption utilized on the latest version of IMSI has all prevented people from cloning them. If anyone wants to read anymore about this look up LE's use of Man in the middle attacks, specifically Stingray's, Cell Site Spoofing and privacy advocates and the criminal world seeking to stop them.
Just another quick comment about smartphones.
If BK more recently deleted anything on his phone LE will likely be able to recover all of it in a unstructured state, fragments of it or references to it. The only way to really avoid this is to use specialized tools/apps or to override every single bit of available hard drive space multiple times over with new data. Effectively wiping out anything that might have been stored on a sector somewhere by the operating system.
Here goes such a tool
BitRaser Wipes Data Securely Using DoD Standard & Helps Achieve Complaince with Laws & Regulations like EU-GDPR & CCPA.
www.bitraser.com
I'm sure the cell phone equivalent is out there somewhere but keep in mind that this is only the first step in destroying a hard drive. After they are confident that a tool like Bitraser has wiped the drive they usually drill it full of holes, shred it in a hard drive shredder, and might even melt it. There's a reason they go through these lengths....
Again, MOO and only mine.
IMO if BK did do it and is successful in wiping out all remnants of any sinister data then LE could look at the places collecting crazy amount of user information often unbeknownst to said user.
First, Go ahead and Copy and Paste this link into your browser...(this link is showing a preview but it's Google's GPS timeline and will likely only work for people clicking on this link from an Android device or if you're a Google Maps on iPhone user)
Code:
https://timeline.google.com/maps/timeline
Then copy and paste this one here.....should work for all Google account holders...even if you don't have an Android device. Unless you've explicitly turned this feature off.....
Code:
https://myactivity.google.com
If you have a Google account and nothing appears under either of those links...CONGRATULATIONS!
2 months left! Then we'll know more!
Edit/Update: I don't want to edit this into the stuff I wrote above because I don't have the time to go over it. But if BK was a frequent user of Google Maps in the area (Maps would recognize this and maintain the area in it's cache for quicker access) or explicitly downloaded the map to his cellular device (option on Android). He could use Google Maps to navigate without needing to have cellular turned on. GPS is independent of cellular and is a phone to satellite / satellite to phone connection. Even turn by turn directions would still work, it just wouldn't utilize live traffic data. The cellular network is only involved to enhance GPS data (surrounding POIs, time you leave for work, traffic etc).