Much to like, and a few things to nitpick about. Practically faultless direction, cinematography and pacing. Some terrific performances from the support actors. Many of the images are memorable and/or shocking.
There are problems with the script and performances of the lead actors. Despite being a true story, some aspects of the story lack credibility, especially upon reflection after the film finishes. The lead actors play a disturbed young man on trial for murder and a young female psychiatric assessor. The best I can say about their performances is that they are competent. The assessor spends the entire film wearing an expression of puzzled anguish which varies only slightly. The disturbed boy fares only a little better.
In another film, these criticisms could have sunk the whole thing. But the direction and cinematography are of such a high calibre that these problems are almost completely glossed over. The film starts a little slowly and has a few confusing viewpoint changes, but the interest builds up and never lets go. The story gets you in, becoming involving and even enthralling. Much of the story is courtroom drama and it is very talky in places, but this is unavoidable in a courtroom drama.
Some of the support actors deserve special mention. The prosecutor is played by Japan's top Shakespearian actor, and he was so good that I wish his part had been made more substantial. The detective who seems to know the full story about the disturbed boy is a loathsome piece of slime, whom I hated more than the accused, and the part is played to perfection. And the defence lawyer is played with straightforward sincerity and good sense.
If this sounds like a mixed review, it isn't. Keiho is perhaps the best Japanese film I've seen this year.