Was someone or the SO chasing him, as in trying to catch up to him?
No doubt pre- impact., impact, and final rest investigation of the vehicle accident scene tells the tale, if done properly and I would expect such from LSP.
Has the family requested and received the accident report? If not, the insurance co. would have it.
What exactly is meant by JPSO pinged his cell phone? Did they actually do that independently or just had documentation of pings from carrier via warrant?
Intoxicated/under the influence drivers can walk long distances.
I have seen them hit a car parked on the shoulder of a major State Highway, completely sever the right front wheel from their vehicle, drive on about 3/4 mile, veer off into a "levee" with a R/R track on top and crash to a stop in the embankment.
Their windshield was badly broken and the little spare change holder in the center console was full of blood.
I drove 2 miles up the Highway to the closest bar that was open that time of night/morning and he was sitting at the bar drinking.
Having run the car license plate and realizing I knew him, I said xxxxx are you ok? He said yes, why? I said you've been in a heck of a wreck, there's struts, bumper, plastic and your right front car tire and rim stewn 3/4 of a mile down the Highway......He said well, you know I do remember a bump.
The point is DUIs can walk away for long distances, but sooner or later they sober up and report the car stolen or are found safe in some way.
No other contact, no other financial transactions, no other signs/evidence of a normal life isn't a good sign. Did this PI talk to the 911 caller?