Both movies are about the interactions and relationship between a young girl that is neglectd by her family and an unusual person.

Similar feel, both take place before and during WW2, both are about family connections and the lives of citizens during war. One is a movie and one is a drama. Boku ga Warau to is brighter

There are mock trials (also actual trials in Law School) shown in both, the investigation part then used in the trial, the mystery of what actually happened throughout

In Law School the characters are law school students so it goes more in depth with the law and the procedures while Solomon's Perjury happening in a high school, the trial is a little less professional