Crime Writing: Blood, Bodies, and Bugs always preach that it’s crucial we get our facts right in crime writing, especially during the investigation scenes. For a writer like me, someone who includes forensics and investigative procedures in all my stories, research is not only necessary, but it’s an important factor in how well my stories ring true. Personally, research is one of my favorite parts of storytelling. I spend hours reading articles that relate to my subject matter.

The trick is to use what we find in a creative way. Nothing bores a reader than a bunch of facts. There are many ways to do this. You could have one character teach another, which is what I did in Marred. Or, you could have a detective watch an autopsy, or have the medical examiner explain what he found, which is what I did in Wings of Mayhem. You could show the detectives collecting evidence. Or have crime scene investigators discuss what they found and why it’s important. If you choose the latter, don’t have two seasoned investigators discuss what they should already know. Nothing irks a reader more than on-the-nose dialogue.

Here are some fun facts I’ve dug up during my endless crime writing research.

Temperature and Time of Death

Body temperature is measured at the scene to help determine how long the victim has been dead. Our medical examiner or coroner should take the body temperature on at least two separate occasions: before removing the body from the scene and after.

However, if the first temperature reading is identical to the environment, there is no need to take subsequent temperatures. After death, a body cools from its normal temperature (98.6 F) until it reaches the temperature of the environment. The body cools at the rate of 1.5 to 2 degrees per hour. For instance, a body that registers approximately 92 degrees Fahrenheit (33.33 degrees Celsius) has been dead about four hours, but there are other factors to consider.

Factors that affect the cooling rate of a dead body:

  1. The temperature of the environment. For instance, a person found outside in cold weather will begin to cool faster than someone found in a heated room.
  2. The size of the person. For instance, a petite woman, or God forbid a child, cools faster than a huge man.
  3. How the person is dressed. For instance, a heavily-clad person cools slower than a lightly-clad or naked person.
  4. Ventilation: A room that’s well-ventilated could actually speed up the rate of cooling by increasing the rate of evaporation.
  5. Humidity: A body in a humid location cools at a slower rate than one in a hot, dry climate.
  6. Insulation: A body that’s wrapped in something (including excess body fat) cools slower than one that’s left out in the open.
  7. Surface temperature: A body lying on a hot surface will cool at a slower rate than one that’s found lying on a cold surface. Thusly, a body in a hot environment cools much slower than one found lying in a cold climate.

[tweetthis twitter_handles=”@SueColetta1″]Crime writing: use research in a creative way.[/tweetthis]

Entomology and Time of Death

Entomology is the study of insects, and they can tell a lot about the time of death. If your entomologist (not detective!) can determine the age of maggots, say, you know the person must be dead at least that long.

Here are some clues to look for:

  • Flies lay eggs on a dead body, usually in an open wound.
  • Eggs hatch almost instantly, up to a maximum of about 36 hours.
  • Larvae (maggots) stay active from 5 – 20 days, and then transform into pupa. Prior to the pupa stage they crawl away from the body, which is where the largest ones are found.
  • The pupa stages lasts about a week before the fly hatches. Remember to have your investigator collect the pupa shells.
  • The fly begins to lay eggs right away and normally lives about two months.

Important to remember:

An entomologist cannot determine the generation of a maggot by merely examining one. Have the investigator collect the larger maggots, the smaller ones, and the pupa shells. Collect live maggots in a glass jar using a tissue. Don’t have them place the live maggots in alcohol, or they’ll die.

Blood-Pattern Analysis

Blood spatter patterns can add a great deal to a story. Analysis of projected bloodstains can help homicide investigators determine:

  • Whether a violent death is a homicide or suicide.
  • How wounds were received. In other words, what happened when.
  • Who was at the crime scene.
  • General type of weapon used to inflict damage/death.
  • Position of victim when the fatal injury was inflicted. In other words, were they moving or at rest?
  • Whether the victim was moved after the fatal injury.
  • How far the blood drops fell before hitting the surface i.e. floor, walls, etc.

[tweetthis twitter_handles=”@SueColetta1″]Forensics often add suspense to our stories.[/tweetthis]

Key characteristics to include (we choose whether to include all or limit our scope, depending on the scene):

Velocity — A free-falling blood drop. High, medium, or low, depending on which weapon was used, and how.

Volume — The volume of a single blood drop is 0.05 ml.

Size — The size and edge characteristics of blood drops determine the velocity. A normal drop will range between 15 mm (5/8″) and 19mm (3/4″). The smaller the drop, the higher the velocity. Medium velocity, say, could be caused by an axe or hammer, where high velocity could be from a gunshot.

Shape — The only accurate way to estimate the dropping distance is to conduct a series of experiments using different weapons. Which could be an intriguing scene.

Surface characteristics and spatter — The surface where the blood fell impacts the spatter. The harder and less porous the surface, the less the spatter results. In Marred, I used an unpolished, un-sanded floor to make it harder for my sheriff.

Direction — Relative to where the victim was at the time of the blow. In general, if the spot is round, the blood was shooting at a 90 degree angle. Oval or tadpole shape would be less than 90 degrees. The points, or tales, show directionally. Meaning, the source of the blood. To give you a better understanding, I included the blood spatter scene from Marred in one of my guest posts,  entitled Edge of Your Seat Psychological Thriller on Entertaining Stories. Castoff blood will streak across the floor, indicting the extent of travel.

Identification Determinable by Blood

The appearance of blood can vary depending on the age of the stains, as well as other factors. By testing the blood the detective can tell whether it’s human or animal, and often right at the scene with a test kit. If the blood is from an animal, it is possible to determine the specific species. If it’s human, the dried blood is then classified into one of four major groups: O, A, B, AB, in order of incidence. And then subgrouped into M, N, MN, and Rh factors (positive or negative). This involves measuring the antigen-antibodies. The latter subgroups are dependent upon the age and condition of the dried stain.

DNA Defined

DNA (deoxyribonucleic acid) — is the genetic material found in body cells. The DNA molecule contains all the genetic information from that specific species. The odds that someone has the same DNA, apart from identical twins, is around one in a trillion. Sorry, but this is not the way to confuse your detective!

As always, check your facts. If you’re lucky enough to have someone in the coroner/law enforcement field, run your questions by them like I do with my dear friend, collaborator, and new critique partner, Garry Rodgers (*winks at Garry* Got your six, buddy!). BTW, his site is chockfull of valuable information for crime writers, including a free guide, How to Write Deadly Crime Fiction.

Over to you. What interesting facts have you found during research?



About Sue Coletta

Member of Mystery Writers of America, Sisters in Crime, and International Thriller Writers, Sue Coletta is the bestselling, award-winning author of psychological thrillers and mysteries. OOTG Flash Fiction Offensive magazine published her flash fiction and her short stories are published in numerous anthologies and collections. InSinC Quarterly featured her forensic articles about Radiocarbon Dating and Skeletal Differences. In 2017, Feedspot awarded her Murder Blog as one of the Top 50 Crime Blogs on the net. Sue's also the communications manager for Forensic Science and the Serial Killer Project. As a way to help fellow crime writers, Sue created a team of crime experts (detectives, coroners, police captains, etc.) and founded #ACrimeChat on Twitter. She's also a proud member of the Kill Zone, where she blogs every other Monday.


  1. Interesting stuff. Doubt if I’ll ever write a detective or mystery novel, or anything that requires such detail, but I’ll bookmark this for future referrals. Research for me generally concentrates on regional idiom, past and present, popular entertainment forms and figures, pastimes, commercial products, social-political landscapes, hairstyles and clothes. Hmm. Now I’m thinking of trying to write a detective tale. Cool. Thanks. 🙂

    • You’re welcome, Ojo. Glad I could help. If you do decide to write a detective story, you don’t need to make it a police procedural. Many authors breeze over the technical stuff. However, I believe by arming ourselves with knowledge in pertinent areas, even if we never use the information in our story, it gives us more insight into our character.

  2. I mean, investigating isn’t a joke. I think in so much fiction, investigation and discovery of elements vital to the inquest is often so easy. And I don’t understand why, since being accurate is so much more intersting and fascinating.

    It’s the same with history. I see lots of writier treating characters acting in a historical context as if they were in the XIX century anyway. Granted, having characters acting like they probably would have in their time it’s work, but if you pull it out it’s so much more fun to write and I think, more fun for the reader too.
    JazzFeathers recently posted…8 Sentence Sunday on Dieselpunks #54My Profile

    • I couldn’t agree more, Sarah. Research is work, but I love it. Personally, I think writers who don’t research their era or character’s job are being lazy. Especially, I would think, for historical novels. All they’d have to do is visit your site, and their characters would become so much more real. 😉 Actually, I should add your site to the Crime Writer’s Resource page because there are many who write historical mysteries and such. I’m diving into Patricia Cornwell’s Post Mortem, and then I’ll add the link. Have an awesome day!

  3. Thanks for the info!! Sometimes I don’t realize how much goes into an investigation.
    Traci Kenworth recently posted…Book Talk…10/16/15My Profile

  4. Thanks for the nod. Research is very important, but has its limits in my fiction. It needs to be plausible, but not perfect. In speculative fiction we’re always going beyond the research. Sometimes the research leads right into some kind of voodoo magic. Not quite the same as crime fiction.

    • Yup. Like your idea mill, which is awesome. You’ve had many ideas that stemmed from that type of research. And you’re right; your research varies greatly from mine.

  5. A wealth of fabulous information, Sue! I found the body temperature information especially interesting, particularly related to environment. That could be used in so many ways.

    Most of my research lately has been related to specific areas and settings, so now you have me thinking what would happen to a body in those settings. Awesome!!
    Mae Clair recently posted…Spooktacular Giveaway Hop and A Halloween Read by Mae Clair #HalloweenMysteryMy Profile

  6. Thank you for sharing this helpful information, Sue. There weren’t either Jane or John Does nor the corpses of Tom, Dick or Harry in my stories – so far; this might well change in an upcoming project. Thanks to you and your useful hints and tips, I can look forward expectantly to the future (and a possible murder in my story).

  7. Your facts are flawless, Sue (as usual). This is really helpful information for crime /thriller writers. I want to throw one little thing out there on decomp time. A great influencer in faster breakdown is the presence of certain drugs in the system, specifically cociane. It amplifies the breakdown time and can falsly indicate a much longer time of death (TOD) than actually occurred.

    Here’s an excellent resource for crime writers. It’s titled “Forensic Science – An Introduction to Scientific and Investigative Techniques” and is exceptionally comprehensive, yet very easy to understand. This one (fairly large) book is like having every forensic expert at your fingertips.

    It’s available on Amazon at

  8. This is such helpful information, Sue! I think it’s absolutely critical for authors to get those details accurate. Even if readers aren’t law enforcement professionals, forensics experts or medical experts, they will sense it if a story isn’t credible. And I think we owe it to readers to do that research!
    Margot Kinberg recently posted…In a Room Where You Do What You Don’t Confess*My Profile

    • My point exactly, Margot. Even on crime shows I’m often pulled out of the storyline by someone saying things like, “I’ll put out an APB” when the correct term is BOLO now. Castle, as much as I love the show, is a big offender of this. 😀

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