If there is anything in his writings that could possibly bring comfort to the Petitos then it should be released to them immediately.
Not for me.
First, I am opposed to the death penalty. Assuming he was guilty (because he never did get a trial that is not legally settled) he should have spent the rest of his natural life in jail. I do not support the government killing people in any way.
Second, a trial might have given the Petitos some information and/or insight into what happened to their daughter because there would be motivation on the part of the authorities to investigate. Now there is none. There will be no trial so the apparatus of the justice system is done with this case and will move on, screw answering questions for the family of the victim.
So yes, it does matter that he killed himself rather than face trial in a court of law. But, clearly, this is a guy who wanted no one but himself to benefit. If you can call bringing about your own death a “benefit”.
Brain Laundrie murdering his own self is just another layer of misery and suffering. It’s another selfish act from a piece of human slime.