Q: I have two characters who are found dead in their house, having been at the center of a fire that turned into a wildfire. Before the fire, a hitman gave them some type of medication that he believed would not be detected in an autopsy to cause them to go unconscious or unable to move while he set the fire around them and escaped. The idea is that I want it to look — on the outside, at least — as though they accidentally caused the wildfire, starting in their home in the forest. Then, it’s discovered that they were, technically, murdered by someone giving them a strong sedative (or something) and they were burned in the fire.
When the medical examiner does the autopsy, what is he likely to be able to notice? I read that bodies are usually not burned completely in a fire, but what would the ME find? What kinds of things would he notice and talk about in the report?
Is there a drug that would have a sedative effect on the characters that would NOT show up in an autopsy? Or something that might show up with a particular test and what reasons could an ME have to run that test?
Kari Wolfe, Colorado Springs, CO
A: You are correct that fires rarely destroy a body completely. The fire simply does not burn hot enough or long enough to completely destroy the body in most structure and automobile fires. The same would hold for wildfires. The body would likely be charged severely on the outside and for several inches down but deep inside most tissues would remain intact. This would allow the medical examiner to test the muscles, brain tissue, liver, blood, bone marrow, urine, and the vitreous humor inside the eyes for various drugs.
Almost any narcotic or sedative would work for your purposes but most of these are easily found with even simple toxicological screening and for sure by more sophisticated toxicological testing using gas chromatography and mass spectroscopy.
More sophisticated drugs are not revealed by a routine drug screen and therefore more difficult to find. Add to this the fact that the medical examiner might have no reason to go to the time and expense of looking for more esoteric toxins if all evidence pointed to the victim having died in the fire.
But what if the victim didn’t die in the fire? What if the victim was already dead before the fire started? This would change everything since in that case the medical examiner could not say that the cause of death was asphyxia from the fire but rather that something else must have killed the victim. In the absence of overt trauma or another obvious cause of death, the ME would likely do more complete toxicological testing.
How would the ME determine that the victim was dead before the fire? One clue would be the carbon monoxide level in the blood. If this is low, the victim was not breathing while the fire was consuming him. If the carbon monoxide level was high it would indicate that he was breathing and had inhaled carbon monoxide, which comes from the burning of wood and almost any other product. The normal carbon monoxide level is less than 5% but in victims of fire it can be 60 to 90%.
Also, if the victim was still breathing during the fire he would inhale soot and heat. The heat would damage the throat and airways and soot and other fire debris would be inhaled deeply into the lungs. Finding these would indicate the victim was alive while the fire burned and not finding them would suggest a prior death. This latter situation could launch a more complete toxicological analysis of the remains and ultimately lead to the lethal drug. Such testing could take many weeks, even months, so that you can delay the discovery of the true cause of death for almost as long as you need for story purposes.