However, 2 miles is a large distance in a city of just 7 square miles. Sure, he was likely in southwest Moscow...
However, that doesn't prove too much. It does establish further investigation and possibly lead to more warrants, but in court I don't know the data they have can be used to prove he was at their house.
Proof is a collection of evidence. They will use the cell data to show that he left his house in Pullman, drove toward Moscow and did something uncharacteristic, which is turn off his phone.
Then they have multiple cameras showing him inside his car (and only him) driving 4X around the neighborhood at 1122 King, at last disappearing from view as he approaches 1122 King Road, where he can't be seen on camera at around 4:02.
But no worries. Because this guy had a knife in a sheath with him, took that knife into someone else's house in the middle of the night; entered private rooms where people slept (committing a felony thereby) and his knife then stabbed 4 people to death. He left the sheath of the knife at the scene,
with his DNA on it. An eyewitness sees a man fitting his description inside the house. Cameras reveal his car (with only him in it) leaving the scene, speeding.
He then drove in a circuitous manner back to his home, turning his phone back on just a few miles from the murder scene. He then returned to the scene a couple of hours later, again using a circuitous route to get home.
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And there will be more:
Purchases, receipts, internet searches, changes in behavior pre- and post-crime, more camera video from businesses than we've seen yet.
DNA inside the car and especially the trunk - because if he took a backpack or any other container, he sure as heck didn't drop it at 1122 King, he took it with him. Personally, I don't think he took anything inside except the knife, in its sheath.
He cleaned up somewhere. I predict blood and DNA residue from victims in his sink trap (being processed right now) and possibly also from the shower drain. While he wasn't soaked in blood, his clothes did have some blood on them and by the time he spent almost an hour getting home, his skin was in contact with the blood too. As was the carpet around the control pedals of his car - we already know the murderer had blood on the soles of his shoes.
If he had left his phone at home, he could at least claim some sort of "I was sleeping" alibi. Being caught on camera driving all around the neighborhood, then disappearing into the parking lot of the murder home at precisely the time the murders are occurring is not a good look for the defense of this person.