Towards the end of Prisoners (2013) in the hospital scene we learn that Keller is being charged of torturing and kidnapping Alex (well the allegations are not clearly mentioned but somewhat implied). That information couldn't be only deduced from detective Loki's testimony. He didn't actually see Keller kidnapping and torturing Alex. At some point Alex should have spoken, too and that should lead to Birches being charged with the same allegations.
We don't see the Birches even being disturbed about this fact. They were happy to have their daughter back and freely walking around.
Is there some plot hole in it or is there some other explanation for it?