Note: This review contains major spoilers so if you don't know about this case you probably need to stop reading here.
If you aren't familiar with the case of the West Memphis Three, you'll probably find this movie infuriating because it's so inconclusive. If you do already know about the case, you won't learn anything new here. It does do a decent job of showing how badly the local police botched the investigation, ignored key details, and basically went on a witch hunt. The movie does make some implications as to what may have really happened, but nobody really knows.
Witherspoon, Firth, and the rest of the cast all do wonderful jobs with the material. The southern accents weren't too mangled, either. I did like how director Atom Egoyan kept the obvious prejudices subtle and the actors playing the accused boys all did great jobs with showing how their own looks and personalities didn't do them any favors with the case.
The biggest problem I had with this movie was that it doesn't really serve a purpose being that it's based on a true story. To date, nobody knows for sure who really killed those boys. That means the audience is left hanging at the end and there have already been numerous documentaries about this case so that a dramatized movie wasn't necessary. Maybe one day the truth will finally be revealed and then this whole thing may be worth revisiting.
Devil's Knot @ IMDb.com