Nope, no PD if not charged. And that's one reason why most DA's don't file charges before they are ready, because they know they have to deal with a lawyer the instant they do.
Many private criminal defense attorneys would offer free services in a high profile case like this one, before charges are laid, with the understanding that LS would hire one of them thereafter, if charged. Most counties will pay a pretty good fee to that private attorney in place of a PD handling the case, as it costs the County an extra amount to pay the PD's office to defend in such a complex case, anyway. There are legal and financial reasons why counties do this, but naturally, it creates a pool of eager criminal defense attorneys.
You'd still have the question of when that could occur. When could it occur? He leaves at 10:13 and does not come back. If you have a theory that he was sleeping in the truck and got out later, well, there would be video of that. HH has employment and employment records.
How anyone could accidentally get enough speed in a garage (or why such a person would be moving a few inches in a closed garage while two other vehicles sit in the driveway - as they clearly do on Monday afternoon - well, I can't see a way for that to happen.
Garage door would have to be closed, the driver would have had to deliberately hit him. Enough to bleed, if you're referring to LS's statements about blood in the garage. All of that without the car going into or coming out of the garage - and LE has obviously put luminol in the house, so they know where the blood is. If there's blood on the third car's tires, they know that too.
This case would be going very differently if there was evidence that someone hit Gannon in the garage with a very slowly moving car. He would have had to be crushed by the weight of the car, not just knocked to the ground and I do not buy that that's an accident.
If that's what happened before LS put Gannon in the truck at 10:13, then Gannon doesn't look too badly injured at that point (and again, since there are two cars in the driveway, it would have had to be done with the garage door closed - very little room to maneuver). LE obviously has video of the entire day and several days before.
We got glimpses inside their garage as well, which was cluttered enough that just to get the third car in there would have required some rearranging (not impossble, but very unlikely) And the whereabouts of each family member on that day (HH was at work) must be known to LE.
Again, that would mean that you have buy that Gannon came home with LS, unseen, and got out of the truck, unseen, and that HH came home, unseen. Someone would have had to move the SUV out of the driveway, since that's the only side of the garage where a car could fit.