Yes, of this I am aware.
Do you think she killed Gannon outside of the truck, then put him back in the truck, and drove somewhere to conceal him?
Or did she kill Gannon, and return to the scene at another point in time to retrieve his body and move him?
Or did she kill him in the truck, and directly conceal his body from the truck to wherever his body is now?
Or she didn't harm Gannon past the initial injury but put him the truck.
Or she made Gannon (still alive) get out of the truck and he then died. (If they find that to be true, they will likely drop the tampering charge).
Since it is the case that there is a tampering charge, I am going to assume that there were byproducts of decomposition associated with one of the vehicles (or some clothing).
Possible sources of cadaverine:
Red Truck (particularly steering wheel)
Rental Car (particularly steering wheel)
HH's white car
TS's own car (less likely)
The piece of wood
The sock
TS's clothing
TS's laundry
Any bags or purses handled by TS on January 27/post-mortem
There would be other sources of course (you can use your imaginations).
The problem is this: cadaverine is not produced in significant quantities at the moment of death. In fact, it probably isn't going to be detectable in any of the above places unless the vehicle or person interacted with the body from 2 hours after death (and really, 8-12 hours would be better).
If TS immediately rid herself of the body right after death or killed him outside of the vehicle, I don't think they'd be able to detect these chemicals reliably enough for trial.
If she moved the body or returned to the body to slightly move it or interact with it in any way, if it was 8-12 hours after death, then yes, probably lots of forensic evidence.
If I were the Defense, I'd be very interested in such matters.
Anyway, I sure do wonder if she didn't return to the body the next day...in a rental car...