She seems to suffer from the same inflated ego problem the rest of the BPD share. Her special training was in the area of sexual crimes and incest, so therefore she solved this crime as soon as she saw John carrying his child.
Steve on the other hand, had a tense relationship with his mom, which had to mean Patsy, being a mom, killed her child.
Myself, I have a fear of intruders sneaking in and taking anything, so therefore IMO it was an intruder. Some fear elves, others think 9 yr old boys are evil, clowns of course have always been feared by many, maybe we all think we have the answer based on our intuition and are not different from Arndt at all? Lord knows there isn't any real evidence, heck there's dna in her underwear that can't be connected to this crime. Might be a first in history, but that's how this crime has been from the beginning, a maze of factoids, nothing substantial or credible can be counted on ,and someone is in charge of the decision as to what is evidence and what isn't and they're "messing up". Years have gone by, they aren't going to solve it, so any statement made by anyone is as good as yours or mine, or better. Right now, I'll put my money on the elf! Maybe the big jolly one? IMO