This demon-possession horror movie has enough good moments that it's a shame the filmmakers didn't try harder; for every effectively moody scene, there's another that's lazy, twitchy, or shopworn. The morgue setting of The Possession of Hannah Grace, with its motion-sensor lights that keep flickering off and on, is great, and it's mostly used well (though not as well as in another morgue-set horror movie, The Autopsy of Jane Doe). The creepy factor is high, and whenever something is just about to happen, director Diederik Van Rooijen and screenwriter Brian Sieve have things under control. But when they actually happen, the camera spasms, and the editing lurches, as if attempting to cover up the fact that we've seen all this scary stuff before, from jump scares to things suddenly whisking by.
That said, the cast is well-chosen and appealing, especially Johnson as the titular possession victim, though it's regrettable that she couldn't have been used better or more practically. In real life, she's a dancer and a contortionist, and while it appears that, here, she's doing some of her own unusual moves, Hannah mostly comes across as an uninspired digital special effect, with added clicking "skitter" sounds -- borrowed from many other horror movies -- for extra creepiness. Overall, The Possession of Hannah Grace isn't truly terrible, but it could have been more muscular if it only had a bit more "exorcise."