Mental Atrophy
Banned
That article didn't really answer my questions, but it lead me to a couple answers on the Twitter of this Michelle Dauber:
So we presume it was addressed to the court, and was in the record prior to sentence. Seems it was after verdict, tho(?).
Correct. The verdict was on May 31 and the sentencing on June 2. The father read the letter during the sentencing. Here is a copy of the full letter.