I get what you're saying, but do we even know what they found in his car, the one that he abducted her in? If so I've never heard any details.
No, but I'd think (and I'm not a lawyer), that if they had evidence of great blood loss in the car, for example, they would have brought murder charges to the table, not abduction charges. Someone (Coy?) did speak to "voluminous" evidence in the car. Still no murder charges, or even assault charges.
But where are we going with this anyway? Oh, I remember (sorry, tired) to hope that any assault happened in the house for there to be "voluminous" physical evidence remaining there.