<em>He thinks it was pathetic. </em>This is the correct option.
The speaker , the attorney, wants to convince the audience that the crime was the result of miserable or poor mental conditions -"..the weird actions of two mad brains."- For the speaker, the two teenage boys were the victims of their own troubled minds; they just followed their childish and weird impulses- "...Planning where every step was foolish and childish, .... been planned in an hour or a day;.."
These options are not right:
-He thinks it was unimportant (Ths speaker thinks it was miserable. He thinks the murder was unimportant: "... the least part of it...")
-He thinks it was unforgivable. ( The attorney does not refer to any memory effect).
-He thinks it was clever. ( On the contrary, he thinks it was foolish. The crime was committed by childish and troubled brains).
