It has been many years, but when I was a surgical resident, we would rarely, if ever, obtain blood toxicology for trauma patients. For the most part, it simply wasn't relevant for the immediate care and stabilization of injured patients, so it was never a medical necessity compared to other labs and tests needed. As an example, a classic teaching question for students and residents was that if you could only get one lab drawn on a trauma patient, what would it be? The answer is a type and cross, which is the lab we need in order to get their blood type and antibody cross-matching in preparation for a blood transfusion.
If the police requested a blood toxicology, there was a separate mechanism for doing this, but we as the health care providers were never required to order it for them.
Practices may be different now and there are probably different laws/regulations for each state and municipality, so please take this in context.