IMO whether TH accidentally hit Athena, purposely hit her or didn't hit her at all is irrelevant as far as the Capital murder charge goes since it's clear (by his own admission) that he intended to murder her and he did in fact murder her. He had plenty of time between trying to break her neck then strangling her to stop and do the right thing - call 911. And if his intention from the getgo was to abduct Athena, well, he did.
IMO it doesn't matter if he "panicked" or whatever story he wants to spin; according to Texas law he committed premeditated murder of a child - during a kidnapping no less - which automatically becomes a capital murder charge. No defense attorney can defend not one but two separate attempts to end Athena's life. And heaven forbid if he SA'd poor Athena.
JMO I believe this is a clear cut case. Oh, we may see the defense requesting a mental evaluation and maybe even try for some mitigating excuse, that's par for the course. I believe he's gonna get the DP. MOO.
Edited due to my responding to the wrong post which may cause confusion. I removed the link to that post. Sorry about that.