Why though? Why in the car straight away?
Seems unlikely, when this guy is a sex pest. He'd likely take her home, everything is fine, phone is off so she isn't disturbed, doesn't have to answer anymore texts. Disagreement occurs in the throes of some sexual encounter or attempt at a sexual encounter.
As per the Utah statute ;
There's literally no reason for him to whack her in the car, when it's pretty obvious that he wanted some kind of sex.
I don't think he hit her over the head in the car either. It's so unlikely with the torque that is required to cause a decent penetrating head injury, as is evidenced by the 5cm fragment of skull missing.
Nevermind the fact that if a wound is to that degree, you will likely have brain matter coming out. Her scalp was gone. He is going to have to carry her inside the house with brain matter and blood leaking from her head? The police would have seen evidence of that on the driveway, no matter how hard this creep tried to scrub it away. It would have leaked *everywhere*.
It's just isn't logically or logistically reasonable.
Given that he gave away the mattress, he probably had some kind of sex with her or had her on the bed, committed the "kidnapping" aspect in conjunction with this and then in some kind of rage - he belted her over the head.
JMO, but logically and by the letter of the Utah State law, I just can't see how any of it occurred any other way.