You picked the wrong house, bub.

I looked up the case details after seeing this episode, and you're right - it was completely re-enacted, even the shadowed confessional parts from "Kate." I'm trying to find the link where I read the explanation for doing it that way (it struck me as odd since "Donna" is dead and therefore not a danger to anyone anymore), but I think it said that the real "Kate" wasn't actually involved in this show at all, and that ID recreated the crime using file footage and police interviews, without having access to the real people in the feud, unlike their usual episodes. So essentially they had to use an actress to stand in as "Kate" and read lines based on her statements to law enforcement.
I was surprised to see that this happened back in 1999, too - much longer ago than I realized! If you're interested, just search for "Pacifica van bomb" and you'll find the newspaper coverage of the case. The show seems to have stuck pretty accurately to the details. What a story!

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There was another thread about this a while ago, they found LaDonna's hand on a neighboring roof months later.
http://www.imdb.com/board/13951130/board/flat/250856308
The real story of "Donna" and "Kate"
http://www.sfgate.com/bayarea/article/Bomber-s-Ex-Neighbor-May-Have-Been-Target-2950936.php
http://www.sfgate.com/bayarea/article/Pacfica-Woman-Says-Tiff-Grew-Into-Threats-2950547.php

Yes, another poster and me said the same thing. IMHO it was someone else's voice reading her words/script.