they can still have a funeral while awaiting toxicology results. the autopsy will have checked her vital organs like the heart, to check if it was a heart attack, the liver, to see if it had completely failed, so they would have weighed it. once all the main body organs are assessed as not to be the cause of death, that would leave the possibility of possible drugs in the system. so biopsies will have been taken from the liver, blood samples taken, and other biopsies from the body. these all take time, and it's not a case of finding say, heroin in the system, they have to check the amount that was in the body, perhaps not enough to cause death, so they need to check for other drugs that may have been taken that when mixed with alcohol or another drug, can be fatal. i know this sounds hard, but because she is dead, there is no rush to get the results back. labs can get toxicology results back in quick time, say if somebody is in A&E and arrive unconscious, and there are suspicions that drugs could be involved, they can test them straight away. you need to understand that forensic labs are very busy places and are often under staffed, so, although Amy is famous, and everyone is speculating about the cause of her death, there are still people getting tox tests to stop them from dying. ruthless as it may seem, a person who has died, does not have priority over those who are alive and trying to be saved, famous or not.