Estimating the Time of Death: Rigor Mortis

Body in full Rigor Mortis

Rigor Mortis, like Livor Mortis or vitreous fluid, is a post-mortem change in the body that may allow investigators to establish an approximate time since death. A few hours after a person dies (and the circulatory system has stopped) the joints of the body begin to stiffen. As they stiffen they become locked into whatever position they were at the time of death (dead bodies aren’t supposed to move right?). The process is affected by temperature but as a rule of thumb for an indoor crime scene the process is noticeable after about three hours and reaches its maximum “stiffness” after about 12 hours. At this point it is very difficult to straighten the limbs and it seems as if you’d need a sledgehammer to bend them in another direction. The joint stiffness will slowly dissipate from this point leaving the body completely after about 72 hours.

One downside to the process is getting the body to fit into a standard body bag. Aside from providing another condition to estimate an approximate time since death, Rigor Mortis is also helpful in understanding the victim’s body position for crime scene reconstruction. Most people choose to avoid dead bodies unless it’s their job. So aside from first responders and the medical examiner why would someone else move a body? Of course, there is always the possibility that a family member or friend who discovers the body may try to administer some form of first aid but that isn’t too common with bodies in Rigor. Another possibility is an unscrupulous passer-by when your victim is found outdoors. Not to stereotype, but imagine a homeless person or drug addict finding the corpse of a well dressed businessman laying in the bushes of a field or something. It wouldn’t be that big a stretch for them to roll the guy and go through his pockets would it?

The last and perhaps the best possibility for your novel is having the killer come back.  Returning to the scene of the crime is a high risk move but it happens. Murders are a messy and chaotic act in which your bad guy will likely be rushed. Fast forward several hours and the killer will likely be going out of his mind reliving the events (unless he’s a sociopath of course). As the killer plays the events over and over in their head they start to second guess themselves. Did I leave anything there? Will the cops believe she really shot herself? Stuff like that. For some killers the stress is unbearable and they make a decision to return and do damage control.

This is great news for CSIs and for authors because any action they take leaves more evidence for us to consider.  Let’s say a victim was hit over the head with a frying pan while they laid in bed and died. Then, six hours later, the killer returns and decides that they want to stage the crime scene to look like the victim fell down the stairs and hit their head. Sounds reasonable to a dirtbag right? But when they pull the body from the bed and toss her down the stairs her body is going to be outstretched and inconsistent with what we would expect to find in an accident. Not to mention all the other evidence they will likely create in the staging process.

As an author you might consider the body position to be a key clue to discovering the place where the victim was killed. For example, maybe your victim is in a sitting position but reclined at an extreme angle. That may match the reclined driver’s seat of a car discovered in another part of town. In such a case the killer may have returned to separate the body from the car because they felt there was something about the two that would point towards the killer’s identity. There are a lot of possibilities at your fingertips so role play a bit and have some fun with it!

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About forensics4fiction

Hi there. Thank you for visiting my BLOG for crime writers. I hope you will find it interesting. I would love to hear your questions and thoughts regarding forensics and criminal investigations. I hope that the information here will help answer your questions or ignite your imagination. I am a retired senior criminalist with 15 years of forensic experience. I have served as the president of the Association for Crime Scene Reconstruction, Rocky Mountain Association of Bloodstain Pattern Analysts, and the Rocky Mountain Division of the International Association for Identification. I am triple board certified in forensic related fields and one of only 40 board-certified bloodstain pattern analysts and 80 board-certified footwear examiners worldwide In addition to writing over 60 scientific papers, I have worked as the editor of the Journal of the Association for Crime Scene Reconstruction, been interviewed by and consulted for television, books, magazines, and newspaper articles including documentaries on the Discovery Channel and National Geographic.

Posted on August 19, 2011, in The Autopsy and tagged , , , , , , , , , , . Bookmark the permalink. 15 Comments.

  1. Being an avid reader of murder mysteries, it seems that the rigor mortis portion of death has often played an important part in the mystery. This seems especially true in older mysteries (Agatha Christie, etc.) I would guess that is because in newer mysteries, while rigor mortis may be important, there are so many new technological tools to help crime solving, that rigor is not as important as it used to be.

    However, being a writer of the old school, I still find rigor mortis in a body to be a “fun” way of expanding a mystery and eventually solving it. Thanks for the info, Tom.

  2. Hi Sandra, you are right that advances in our understanding of the processes following death ahve allowed us to improve our estimates of the time since death and Rigor is just one of many “tests” that can be used to arrive at that estimate. It is still an important aspect but one in a chorus of data. What is your favorite Agatha Christie story?

  3. Hands down, The Murder of Roger Ackroyd – after that, Murder on the Orient Express.

    When I was writing my reply above, my mind went blank regarding some favorite murder mystery authors. I remembered some of them now: Sue Grafton (with the alphabet mysteries), Mary Higgins Clark and, more recently, her daughter Carol Higgins Clark, and Lillian Jackson Braun’s “The Cat Who…” series. My all-time favorite mystery author is Rex Stout and his Nero Wolfe series. I could go on and on, as I’m enjoying this trip down Memory Lane.

    Even although I’m now more immersed in fantasy and science fantasy, I still enjoy the occasional mystery. One of the most fun mysteries is I, Robot, written by Isaac Asimov. I read these mysteries long before the movie ever came out.

  4. Yeah, I watched a few episodes, but I felt that the actors didn’t do the characters justice. In all fairness, I thought these characters might be hard to emulate…you had to know them thoroughly to understand what made them tick.

    The book series actually was a three-generational thing in my family. Started by my mother, she passed her NW books on to me at an early age. Even at 7 and 8 I avidly read almost anything I could get my hands on.

    Then my daughter became interested in the NW series, and I knew what to get her for birthday and Christmas for a few years. In retrospect it’s surprising that it was just the females of our family–my dad, although an avid reader, wasn’t interested, nor is my son or husband. Oh well.

  5. Tom,

    Quick question about what happens after death. I’ve have heard that a body, on its own, can move after death because of gases in the body. I’ve heard they can sit up, scream and even moan. Is this true or folklore?

    Thanks,
    Kim G.

    • Hey, Kim – I’m sure Tom will have a great answer, but I’d like to share what a former boyfriend experienced.

      George was an new officer in the Ontario Provincial Police force (something like State Troopers in the U.S.) He had never picked up a body before. One dark stormy night, he was ordered to go to a remote area to pick up a body near a lake.

      He drove there, not particularly worried about the darkness of the night. After all, he had good carlights and a good flashlight.

      He found the body all right and, to the tune of the waves crashing against the lakeshore, hauled the body into the back seat of the cruiser. Then he turned his cruiser around on the deserted road and headed back to the OPP detachment. About a quarter of the way back. He thought he heard a noise from the back seat. The hair on his neck prickled.

      He listened more intently, one ear cocked towards the back seat. Suddenly, there was a shrill scream and the body sat up in the back seat.

      George said he almost had a heart attack himself, slammed on the car brakes in the middle of the road, jumped out and unholstered his gun. He said if that son of a b…. wasn’t dead, he’d make sure he was.

      It was a funny story when he told it, but I can imagine the scare he had at the time wasn’t funny.

    • Hi Kim, sorry I just got back into town. Interesting question. I have never heard of such a thing, even as folklore. While I’m sure that this idea may be rooted in some peculiar case, I think this is made up. It’s true that bodies can make gurgling sounds and even higher pitched sounds as gases are released during decomposition. I’ve never heard anything approaching a “scream”. In order for the body to “sit up” (assuming from a supine position) the muscles would have to contract which takes electrical stimulus. Even if this would happen I don’ see how the body would stop at an upright condition rather than hyper extending towards the toes. It sure does sound creepy though. Now bodies can and do move following death but the movement is pretty small. The body or head may roll especially after investigators start messing with it. I’ve never seen anything that would “freak me out” but it’s easy to let your imagination run wild, especially in the morgue at night. I checked my library just to be sure and I don’t see any references. I’m sure if this was a “normal” thing we’d hear about it. If nothing else, it would keep us from soiling ourselves :). Hope that helps!

  6. Sandy,

    Funny! I had a teacher tell me that, as well. Your’s sounds like a great scene for a book! So your saying it true right?

    Kim

    • Well, I didn’t witness it myself, but George was my boyfriend at the time and I was pretty sure he wasn’t making it up. He was making it sound like a funny story because otherwise he would be admitting that he, a macho man like himself, had been afraid. Still, I detected the earnestness of truth in his words. Plus which, he swore it was true :)

  7. Thanks Tom. My husband owes me a night out, because I didn’t think it could happen! Your are a great resource! Have a nice night.

    Thanks Again,

    Kim G.

  8. Just a quick question: I understand that rigor mortis enters the body from head to toe and that it exits in the same order, but have just heard on some detective show that it exits the opposite way, i.e., from toe to head. Which is correct, all other conditions being the same?

    • The “flow” you are describing is a bit of a misnomer. Rigor affects muscles at the same rate and is more influenced by temperature. Smaller muscle groups (such as those found on the face) will be affected by this process more quickly than larger muscle groups (like the thigh). So while it appears that it “spreads” or “flows” it’s not like a wave or anything. The body position of rigor is not necessarily as important as the “degree” of rigor coupled with other factors. How are you planning on using this in your novel?

  9. Dear Tom Adair,

    I work as the photo editor for a series of history books published in Denmark, Sweden, Norway and Finland. We have found an image on your website, and we would like to use it in a chapter in one of the books.

    The book is about historical villains, and we would like to use the image in a chapter about the history of forensic science.

    Links to the image:
    http://forensics4fiction.files.wordpress.com/2011/08/rigor1.jpg

    http://forensics4fiction.com/2011/08/19/estimating-the-time-of-death-rigor-mortis-2/

    We would like to use the image on 1/6 page on a spread inside the book.

    May we use the image? Can you tell us where you got the image from, and who might hold the copyright to it?
    And do you have a digital file, 300 dpi, at least 9 x 11 inches, jpg-file or tiff-file, you can send to us?

    Aug. 21, 2013 is our deadline, so if we can find out this week whether we can use the image, it would be great.

    Any help will be greatly appreciated.

    Many kind regards, and please let me know if you have any questions.
    Jasmina

    Jasmina Nielsen
    Photo Editor
    Highlights of History
    Bonnier Publications
    Copenhagen, Denmark
    Tel. +45 39 17 24 00
    Email: hbv-billedresearch (at) bonnier.dk

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