The idea is that both families (the murdered and the murderer's) have suffered because of the crime. It is appropriate for the murderer's folks to say how devastated, how affected they are. But! In the process, they are also expected to at least acknowledge the pain and devastation of the murdered's family.

They are not expected to get up excuse the murderer. They are expected to at least acknowlege the pain that he/she caused to the true victims -- the dead and his/her family, friends, associates, etec.