pearl21:Does DAN try to get toxicology reports from fatal cases to see what medications were in the victim's blood?
Back when I was an autopsy tech, the pathologists would request toxicology screens and levels of therapeutic drugs the patient was known or suspected to have been taking. The screens were quite general, and were limited to common drugs of abuse (some of which were also therapeutic drugs such as barbiturates or benzodiazepines). Sometimes, heavy metal panels or insecticide screens were requested.
Too many drugs exist for it to be practical to screen for every possibility at autopsy or clinically, so a tox report will only ever let you know if specific drugs that were looked for actually showed up, not a "real" answer to the question of what drugs were in the system.
You might also be surprised at how very few autopsies are performed. Many "ME cases" aren't even necessarily autopsied.