In some instances, the cause of death may be readily apparent at the time of autopsy, but the manner of death is not known. An example of the latter is a person dying in a house fire from smoke inhalation and burns. We can see soot in the airway, and we can see burns. However, we cannot tell from autopsy what started the fire. That answer must come from the arson investigation (which is outside the purview of the medical examiner).
As manner of death (homicide, suicide or accident) will then hinge on that determination, we must await conclusion of the investigation. Other examples of the latter are head injuries where nobody saw the traumatic incident, and some close range gunshot wounds (where gunshot residue analysis, range determination, firearms examination, and police investigation may all be necessary to arrive at a determination between suicide, homicide or accident).
Furthermore, in order for accredited forensic toxicology laboratory results to be considered legally valid the results must be confirmed by two types of tests. Toxicology tests will take longer if multiple drugs are involved, if unusual drugs are involved, or if the person is decomposed.
Finally, one must consider the possibility that the pathologist's initial suspicions are not confirmed. For example, if the pathologist suspects drug toxicity but the initial toxicology report reveals only low levels of drugs or no drugs at all. In these cases, the pathologist may submit additional tissues to reevaluate specific parts of the heart muscle or brain, while at the same time consulting with the toxicologist to pursue testing for more unusual or exotic drugs that weren't originally analyzed, while at the same time asking the police to return to the scene of death to ascertain more information, or perhaps to interview additional witnesses. Each death is different, and the findings in each case are different. Additional follow-up is determined as results are obtained. Obviously in such multi-step investigations the process may be lengthy, and the requisite time necessary may not be entirely under the control of the pathologist.
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Why would your door be unlocked and left wide open?!
