For Crime Novelists
(Video recording at the bottom!)
I recently watched a detective show where the coroner stated the time of death was 12:32.
It’s incredible they knew the exact time. In fact, it’s nearly impossible to know exactly when someone died.
I’m sure you’ve seen it many times, where a watch was broken and that’s the explanation for the exact time of death. But is it good enough?
What if the watch was broken hours before they were attacked? What if the watch was symbolic or a family heirloom that was broken years ago? What if it constantly loses or gains time?
Time of death is a best estimate game.
A medical examiner or coroner will give detectives a time of death range of about 2 to 4 hours, but there are circumstances where an estimate of days is the best they can say. Longer estimates happen mostly when a body is found long after death.
But there are many ways to determine time of death.
Body temperature
Rigor mortis
Livor mortis – lividity
Degree of putrefaction
Stomach contents
Corneal cloudiness
Vitreous potassium level
Insect activity
Sound gross? It is a bit, but when you approach it scientifically, it’s not so bad.
I find it fascinating. Yet, I wouldn’t want to be an ME or coroner. 😊
Let’s discuss body temperature first.
Body temperature
Body temperature is where most examiners begin. The body temperature is taken either rectally or from the liver, which is more accurate, but an incision must be made to get it, it’s not the most common way.
After death, the body temp will level with the ambient temperature. So, a warm environment will affect the body differently than a cold one.
The average rate of body temperature dropping is 1.5 degrees per hour, though there are a lot of other factors to consider.
Weight, clothing, age, environmental temperature and conditions.
Body temperature in hot climates will actually raise to equilibrate with its surroundings.
A body left on a frozen lake when it’s windy and snowing out will drop its temperature way faster than if it was found in a home with the temperature set at 70 and no windows or doors open to cool it faster.
Unless your crime novel is a forensic one, I don’t suggest you need to mention a specific temperature. For that, you may need help from a professional to be accurate.
Otherwise, mentioning the particular difficulties the ME had in determining the time of death from the body temp should be good enough.
“Judging by the wind, rain, and cool temperatures last night, and the victim being well-bundled up, I estimate TOD to be between six and twelve hours.”
Another great help to find the time of death is to evaluate rigor mortis.
Rigor mortis
Rigor mortis, the stiffening and contraction of muscles after death, has a general rule of 12-12-12. 12 hours until the body is stiff. 12 hours it stays stiff, and 12 hours until it becomes flaccid again. But ambient temperature plays a role too.
Higher temps speed up the process and colder temps slow it down. If a body is frozen, rigor may not happen until the body is thawed!
There are also cases where the body had a cadaveric spasm. A spasm locks the body in the posture it was in at the moment of death. This usually happens when an extremely violent or an extremely emotional situation has occurred.
Rigor mortis may be used when body temperature can’t, for example, when the body temp has equaled that of the environment.
Livor mortis
Livor mortis has nothing to do with the liver. 😊
It’s about lividity. Lividity is the staining of tissues, usually purple, but depending on the environment and medications, it could be pink or red.
After death, the blood exits the capillaries, veins, and arteries and pools in the tissues. Gravity plays a huge part in assessing lividity by pulling the blood down.
Livor mortis begins between 30 min and 2 hours after death and hits its at max at 8-12 hours. Fixed lividity happens by 6 to 8 hours. The ME can also tell if and approximately when after death a body has been moved!
Let’s say my character was killed in the bathroom of their apartment. The killer let them lay on their side for an hour while they decided on where to dump the body. Blood will pool toward the side the body was lying on.
The killer takes the body for an hour’s ride out of town in their trunk, where the body is laying on its other side. The staining happens on the opposite side.
Then they dig a grave and place the body on its back. Gravity will pull the blood down, so the staining is near the corpse’s back.
I say near the back and not the back, because when pressed against a hard surface, the blood can’t pool there, so it goes close to the area, but not on the area the hard surface is touching.
Degree of putrefaction
Putrefaction is the decay or decomposition of the body. Like the other determiners, it has a pattern, but that pattern is affected by the surroundings.
Putrefaction happens in two distinct ways. One is self-digestion, the other is digestion by bacteria. Both are faster in warm conditions and slower in cold conditions.
So, while the degree of putrefaction can help with determining time of death, the ME must account for all the factors before making an estimate.
Stomach contents
We get this a lot in crime fiction, especially on TV shows. But stomach contents are usually combined with other information, like witness statements.
The stomach empties on average two hours after the last meal. Protein and fat digest slower than carbs and sugars, but it’s a fair approximation. Alcohol and other medications and conditions can slow or hasten this process.
A witness may say they saw the character eating dinner at 7 pm and their stomach contains nothing. This simply means they died after 9 pm. On its own, it’s not a reliable method for time of death.
Corneal cloudiness and vitreous potassium levels
Cloudy and opaque corneas happen within a few hours of death if the victim’s eyes were open, but up to 24 hours if they were closed.
The vitreous humor is the clear thick liquid that fills the eyeballs, and after death, the potassium levels increase at a constant rate over the first few days.
Both of these are helpful tools but are only valuable in conjunction with other factors. Again, ambient temperature affects both of these processes.
Insect activity
No one likes to think about the critters that devour people if they’ve been left somewhere, but insects are valuable and useful in determining time of death.
Usually, within one hour, blowflies descend. They lay eggs, the eggs hatch within hours, the larvae feed, grow, and molt. Twelve days later, they become adult flies, and the process repeats.
So, knowing the life cycle can aid in determining the time of death, but insects are useful in toxicology too as they can be tested for chemicals contained in the body they fed on. 😊
The medical examiner or coroner will use some of these methods to establish time of death. They don’t often use all of them. Once they feel they are reasonably confident, they won’t continue digging unless there is a suspicion that the time is wrong.
All or none of this may end up in your novel, but it’s important to know what the processes are and how they work together to accurately determine the time of death.
And now that you know, you can use these processes to lead your investigator and readers in the right direction or use them as places for red herrings.
“The ME tech originally estimated the time of death as between 4 and 8 am, but now the ME says, because of the chill last night, it could be between 2 to 4 am.”
“At the house, I couldn’t see the livor mortis on the victim’s backside, but due to the pooling of blood there, I now know she was sitting, probably in a chair, for at least an hour before she was placed on the floor.”
I hope you have found this article helpful.
A special thanks to Dr. D. P. Lyle for his detailed descriptions in Forensics: A guide for writers.
Until next time,
Happy writing and revising!
Kristin Noland – Speculative and Crime Fiction Editor
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