Kevin,
First off, I'm sorry to hear about this...it sounds like no one followed through at the crime lab or with the SA's office, not sure about the police follow up either. I am an officer and part of a specialized crash reconstruction team, all I do is fatal and serious injury crashes. The primary function of their investigation is criminal prosecution. In crashes such as these someone should always be following through until the end, without question!
In our area, and most places around the country, the prosecutors order further testing after a driver tests positive for something. We ALWAYS send the samples out for quantifying data and results...that way there's no question or issues later on in prosecution. This should have begun with the police and crime lab, and been verified by the SA.
Years ago if you tested positive for drugs it was DUI-Drugs, period. Now days the courts want to see what "level" you are at and if it was a contributing factor to the crash. I don't think it should matter, but I'm not the courts and my opinion is worth two cents. If this were my investigation I would blow my lid...I couldn't imagine telling this to any victim's family, and none should go through this.
There is no reason why the results weren't quantified. Yes, it costs about $800, but we're talking about someone's life. I'm sorry Kevin (and family) that you have to go through this...and I apologize for the mistakes that fellow law enforcement and courts have made. If you need anything, don't hesitate to ask.