I am assuming you are talking about my post from this morning. Here is why I think that:
If you watch at about 7:15 or so, they are showing where the bullet casing was found, and where she SAID she shot him. Casings come out of a gun up and to the right..... NOT LEFT.
A couple or three caveats:
1. Jodi Arias is guilty of First Degree Premeditated Murder. She was not abused. Travis Alexander was not a pedophile. Oswald shot Kennedy and 9/11 was not an inside job.
2. Travis Alexander was shot last, as a coup de grace. I assume when he was gurgling and in the throes of reflexive agonal breathing through a cut throat. I'm not proud of it, but I've seen a number of gore site throat cutting videos. It's an excruciating death. Shooting him in the head at that point may be the closest someone as twisted as Arias came to mercy.
In any case, I find it extremely difficult to believe someone could take a penetrating wound to the skull with cavitation of brain tissue and engage in purposeful action. Sure, people have survived head wounds. That doesn't mean they were walking around immediately after.
That said, does anyone have any idea what kind of .25 automatic it was? As it was Arias' grandfather's I would guess it was a an older colt-type with a small right ejector port, but based on the model and the extent of the "full open" of the slide (as with a Taurus, for example) the angle of ejection could be pretty acute. Even with my .45 1911A1 (Colt type) casings have landed to the right of me, to the left, dropped on top of my head.
My subjective experience is that smaller calibers eject further. Longer casings are more erratic when they spin, land and bounce.
That the casing landed in blood tells you the blood was there before the casing. Period. With a single casing you really can't guess as to the position of the shooter. For all we know that single casing bounced off a wall, off the ceiling, onto the floor and bounced again before landing in the blood.
That's all you really need to know: He was already bleeding before he was shot.
Why bring the gun? My impression, based on everything we know about how Arias' mind works, is that it was insurance. Either as part of a half-hearted suicide option, or to deal with the unexpected such as roommates or even another women.