Truman helps prolong the lives of two murderers, giving them false hope of reprieve within a barren prison existence, in order to better understand their crime, and turn his understanding into a non-fiction novel.
He makes good on his promise to portray Perry as more human than monster. The other killer gets far less empathetic treatment. The victims of the crime appear only in horrific flashbacks and crime scene photographs.
Truman is aware of the exploitative aspect of his work. First he needs to keep the prisoners alive, so he can get their story, then he needs them dead, so he can conclude and sell it (his friend Nell sees this dynamic even more clearly). He also sees a lot of himself reflected in Perry. His empathy is real, if tainted. And besides, it's not just Truman who stands to gain by exploiting suffering and violence, but his community of literati, generations of English professors, the makers of this film.
Coincidentally, just a few hours before seeing this film with Dave, I read Lawrence Weshler's essay Valkyries Over Iraq (Harper's, Nov 2005), which looks at how violence and art sometimes feed off one another within the war movie genre. Obviously art is part of life, not outside it, just as language is within the world -- it's not really a matter of one imitating the other. As a Buddhist might put it: parts reflect other parts but the whole is unreflected, because it has no mirror.