If an autopsy is performed, the pentobarbital (or any other drug) will be discovered. Questions about its source could be asked. A suicide note that explains the source of the drug could be very helpful in this situation.
The only method that leaves no trace, even at autopsy, is the Exit Bag with nitrogen (a hypoxic death with helium will be detectable at autopsy). For the death to be recorded as natural, however, the bag, tubing and the cylinder would need to be removed. This is where a possible breach of the law comes in.
Is it better to die in the Morning or Evening?
Regardless of the method, it is generally advisable that the death takes place in the evening. This not only provides enough time for the possibility that the drugs take longer than they expected to work, but it will allow family members or friends to ‘discover’ the body in the morning. Then the doctor can be telephoned and the official paperwork completed by him/her. An overnight death also allows for everyone else in the house to say they were asleep in bed when the death took place (with no one able to prove otherwise).
If there is any doubt about the cause of death, the attending doctor will contact the coroner and an autopsy may be arranged. An autopsy involves the dissection of the body by a pathologist, the visual and microscopic inspection of organs, along with the biochemical testing of body fluids, stomach contents etc.