Her body might have been bones, but there may have been clothing, and since she was under boards, therefore the clothing was protected enough from the elements.
http://www.pbs.org/wgbh/pages/frontline/shows/case/revolution/databases.html
So LA passed the law in Sept 99, now BSL was arrested in April 1999. Not sure he got his DNA or not. I believe it was only prisoners who came into the system after the law was passed that had their DNA taken. What I'm trying to say is I don't know if it was retroactive or not. I believe I heard once on TV that it wasn't retroactive that only prisoners coming into the system after the law was passed had to give up their DNA.
I will say though given he was a T3 sex offender they might have done that upon his release.
Even so, it could also be that since the initial investigation LP case sat in cold case, and probably had a few different investigator's peruse the case but not follow up on BSL.
All this is neither here or there for we will find out soon enough (hopefully) when this goes to trial.
I only mentioned it as I knew it wasn't law at the time, so my theory could be correct. Another angle so to speak to think about.