I believe Dr. Perper did see a single injection site and that is why he asked if she used alcohol swabs when she injected Demerol. But why they (Greta & Baden) think she would shoot it into veins is beyond me. There are other ways to inject it they know this.
Yes - just adding to the confusion - and not stating all the facts.
Let's think about the alcohol itself. It must have to do with what LE took out of the room and something that was missing....something that should have been there if it happened like Howard told Perper that he think it happened. In other words, there's a discrepancy in Howard's story.