Monthly Archives: November 2011
Components of a Shotgun Shell
Clockwise from upper left; gunpowder, No. 8 pellets, blue shotcup, and empty 12 gauge shotgun shell
Shotgun shells are similar to center-fire cartridges with one important distinction; the wad or shot cup. Shotgun shells come in a variety of calibers (such as .410, 20 gauge, 12 gauge which are the most common) and typically fire pellets instead of a single projectile. Having said that, there are shells designed to fire a single projectile called a “slug”. The size and number of pellets varies as well and are designed for specific uses. Size 8 or 9 shot are small BB sized pellets used for target practice and small game hunting while larger shot such as 00Buck are used for home defense and predator hunting.
When a typical cartridge is fired at a crime scene the CSI might look for both the bullet and the cartridge case. The other component (powder) is generally burned up but can be found in a residue. But with a shotgun discharge the CSI may also be looking for the wad or shot cup . Most modern ammunition uses a shotcup which is a plastic “cup” with separate ”petals” which fold away after leaving the muzzle and slow its forward movement (see photo). Older shotgun shells commonly used a wad which was a small fibrous disc of the same diameter as the shell. It’s kind of like a little padded sponge but without the holes and denser. Without a wad or shotcup the pellets would exit the muzzle with much les energy because the pellets can’t hold back the pressure as well as a solid projectile. Shotguns are smooth-bore weapons and generally do not have rifling which means the examiner can not do a traditional rifling comparison like they would with an expended bullet.
Various types of fired shotcups
Badguys will sometimes pick up their expended cases or shells (often referred to as “policing your brass”) but finding the shotcup would be very difficult as it can travel quite some distance from the muzzle (I have found them over 100 feet away). Sometimes, if the muzzle is in contact or close contact with the victim the shotcup or wad may even be recovered from inside the victim at autopsy. Now a firearms examiner can not link a shotcup to a particular weapon but examining the shotcup might reveal what type and size of shot was used and even the manufacturer of the ammunition. This might be important circumstantial evidence to consider when searching a suspect’s home, vehicle, or financial records.
Expended shotcup on ground
Estimating the Time of Death: Algor Mortis
Algor Mortis is the last of the three Cardinal changes occurring to a body following death. The other two, Rigor Mortis and Livor Mortis have been covered before on this blog. Algor Mortis is the postmortem cooling of the body. Technically, it’s the acclimation of body temperature to the environmental temperatures. The healthy human body in life maintains a temperature of about 98 degrees Fahrenheit (37 degrees Celsius). If the air temperature is lower the body will cool and if the temperatures are higher then the body will warm. Typically these measurements are taken by inserting a probe into the liver (at least twice with an hour between). Oral temperatures are not reliable examples of core body temperatures and are not used.
There are a number of things that can affect how quickly the core body temperature acclimates. Some of those conditions include the type and amount of clothing the victim is wearing, or if the victim is wrapped (like in plastic sheeting). Bodies with a lot of clothing will be more insulated from the environment and thus cool more slowly. Body mass also influences temperature change. Environmental temperatures obviously influence this process and some areas see dramatic swings in temperatures in short periods of time. My readers in Colorado are very familiar with this. We can have a white-out blizzard in the morning and have clear skies and 50 degrees F by lunch. If the clothing or wrappings are wet then that will have an influence as well, especially when temperatures swing between freeze and thaw.
Adding to all of these considerations is the realization that decomposition is not a static process. Scavengers (vertebrate and arthropod) can significantly alter coverings and body mass at unpredictable rates. Over the years, scientists have attempted to develop various formulas to estimate the time since death using changes in core body temperature. However, due to the variations experienced during decomposition these formulas are not considered reliable.
As an author, you should probably avoid having characters put too much emphasis on Algor Mortis estimations or readings unless you want to set your characters up to be in error. This can be a useful tool, especially if the character you want to “set-up” is not directly involved in the forensic sciences (like a hospital pathologist or family doctor). You could create some tension between the police, victim’s family, and a hospital pathologist using an over-reliance on postmortem body temperature levels. Your Coroner/Medical Examiner or entomologist character will most likely be able to settle the issue with finality and use other postmortem changes to estimate the time since death.
Examining Light Bulb Filaments
Lightbulb with broken filament (top)
Up until quite recently automobile head lamps, brake and signal lights used incandescent light bulbs (as opposed to LED) containing a filament. The filament is a thin metal wire within the bulb suspended between the terminals connected to a power source. The electricity supplied to the bulb will heat the thin wire until it glows. When metals are heated (especially to a temperature/mass ratio) they become pliable. This is exactly why a blacksmith heats his metal stock in a hot fire while making whatever tool he needs to fabricate. We all know that these types of light bulbs produce heat during this process. That’s what makes the Easy-Bake Oven work right? So when the light is on the filament is hot and pliable. This condition affects the analysis of these bulbs during the investigation of automobile collisions and makes them a very valuable tool to the accident reconstructionist.
One of the things CSI want to know in a collision is whether the persons lights were activated. In a night-time collision the reasoning is obvious. If the lights were off then that fact may have contributed to the collision. Brake lights are another consideration. If the brake lights were off then that may indicate something important to the investigation. I once responded to a scene in which a suicidal man (as reported by the family) drove off a cliff and plunged over 100 feet to his death when officers tried to contact him. The officer claimed he never saw the man activate his brakes as he flew off the cliff. There were no skid marks on the side of the road and when I examined the filaments they confirmed the officer’s observations. So how does this examination work?
In simple terms you can think of Newton’s Laws of Motion which state (in part) that an object in motion tends to stay in motion. In a collision the ends of the metal filament are anchored to the terminals. The wire is heated and pliable so when the vehicle abruptly stops (decelerates) the pliable filament continues to travel in the direction it had been going. Sometimes that filament breaks and other times it simply bends (see photos). This pliability occurs in a fraction of a second so the light doesn’t have to be activated for long periods of time for this technique to be used. If the filament is unbroken or un-bent then that indicates the light was not activated. Now, how can you use this in your novel?
Lightbulb filament bending to the right (as opposed to straight)
Imagine a scenario in which a killer dumps a vehicle into a lake or something to stage a car accident in order to cover up the murder. When your detective or CSI examines the bulb and finds out that it wasn’t activated that may cause them to question the accident premise. Now, in fairness, it could be that the person had a heart attack or some other condition that prevented them from activating the brakes but your Coroner character can address that at autopsy.
The Ol’ “I Was Just Cleaning My Gun When It Went Off” Excuse
CSIs sometimes respond to shooting scenes in which there has been an “accidental discharge”. Most of the time the shooter is your average citizen but sometimes they are in private security or even law enforcement. In a vast majority of cases there are no injuries or injuries only to the shooter (like shooting themselves in the hand or leg). These cases are usually pretty easy to spot. The shooter is often very embarrassed or will offer a laundry list of excuses as to why the gun went off. Such excuses can include…
- I installed a “hair-trigger” and accidentally touched it
- That’s new ammunition and it must be defective
- I dropped it
- and my personal favorite “I was just cleaning it and it went off!”
When CSI’s respond to these calls there are a number of things we look at. Obviously we want to know about the shooter and their experience with firearms but even an experienced shooter can make a mistake. Having said that, the very first rule in cleaning your gun involves unloading it! So offering this excuse is highly suspicious to investigators. So from a crime scene standpoint what sort of things can we determine. First we look at trajectory. Where did the bullet go? For example, if we see a round that goes through a mirror horizontally at about chest or head level what would that suggest? It may suggest that the shooter was “practicing” his “quick draw” in front of the mirror with a loaded gun. If that is the case then it’s easy to understand why the shooter didn’t want to admit to the mistake. The same is true when the shooter shoots themselves. I once had a case where a Don Juan type was showing off to his new girlfriend (teaching her gun safety) and shot himself in the leg. Needless to say he definitely made an impression on her! Whatever the reason, the trajectory of the bullet should approximate the activity described. But trajectory is just one element.
Obviously we also look at the conditions of the crime scene. We look at evidence like fingerprints and the directionality of bloodstains (if they exist). If they claim to be cleaning the gun we would hope to see a complete cleaning kit. Does the shooter have all the necessary tools to clean the weapon? It’s kind of hard to clean a gun without the properly sized cleaning brush (i.e. using a 12 gauge brush to try and clean a 9mm pistol). Was the cleaning kit bought that day (or within the past few days)? Have they ever cleaned it before? Can they articulate how to clean the weapon and walk your protagonist through it step by step? Another issue to address is the time of the shooting. Most shooters don’t clean their guns at one o’clock in the morning. Many good shooters will clean their guns at the range or upon returning home from shooting. This begs the question of why they were cleaning their gun. Did they recently go shooting? Where? When? Can investigators find evidence to support that claim? All of this is important in building the back-story of the investigation. If the person hasn’t shot the gun in months it begs the question why clean the gun here and now?
Trajectory inconsistent with "cleaning"
Rarely, a person might use this excuse in an effort to camouflage a murder or suicide. They may either plant a gun in hand or introduce evidence (staging) to make it appear the person died while cleaning their gun. Obviously, investigators would look at the relationship between the victim and the reporting party. Did neighbors hear them fighting? Is there a history of violence or conflict between them? Assuming that the shooting is an accidental result of cleaning (a huge assumption) we would look at the position of the victim relative to the shooter. A victim shot within eyesight of the shooter (where they can aim) is more suspicious than a round that goes through an apartment wall and hits a neighbor. Although, just because the bullet went through the wall doesn’t mean it was an accident. It could be the suspect was tired of the loud music and fired a round through the wall in frustration (and criminal stupidity).
There are obviously a lot of other things that we may look at given the circumstances of the case but I don’t want to give away too much. The important thing to remember when writing a scene like this is to consider the who, what, where, why and how issues of the shooting. Why here, why now, why them? Does the trajectory “fit” the scenario provided by the shooter? Bottom line…does it pass the smell test? Investigators will be looking for the clues that don’t add up. If it is truly an accident then the evidence should be pretty obvious. But if your character has staged the scene you can use some of the examples below to create clues for your protagonist to find. If you are a gun owner and do a lot of shooting you should be able to think of several more as well. However you choose to use this excuse it can add a nice twist to your storyline and keep your readers engaged.
The Armchair Detective: Case #1 The Traffic Stop
I wanted to try something new with you folks and I’m calling it the Armchair Detective series. Basically, I’m going to post photos and pose questions in order to teach you a little about the investigative process and forensics. This is a little trick I used to use with students and interns and I think it might be fun to try it here with you too. These exercises can be very helpful in teaching individuals how to view and value evidence and as authors I thought you might reap some of the same benefits. So here is how it works. I pose a question or series of questions usually connected to some kind of imagery and then I give all of you several days to a week to respond with your observations. Most of the time you won’t have all the information you think you want or need but that is precisely the same challenge of the CSI. If nothing else, these will provide you with a handy excuse to take a break from writing and exercise another portion of your brain. Ready?
Case #1: The Traffic Stop
Imagine the images below were taken from a “traffic stop” and you are the CSI. What clues can you discern from the content of the images submitted by the officer? Can you tell me anything about the driver? In short, tell me what you see that a law enforcement officer should take notice of. Since this is a theoretical exercise don’t be too concerned about taking a leap or generating a theory. While I am looking for certain answers treat it as if there are no right or wrong answers. Have fun and comment as often as you like. I’ll give you my observations after several days. Good luck!
Defying Common Sense: Partially Suspended Hangings
If I asked you to picture a hanging in your mind I’d bet most of you would conjure up something out of a western movie with the bad guy hanging from a gallows or Sycamore Tree. Hopefully, you don’t have any other point of reference. The imagery of a person “swinging” from a rope can be quite powerful and I understand why novelists choose to use it. But you might be surprised to know that a majority of such deaths are not what we call “full suspension” but rather “Partial suspension”. Put simply, a partial suspension is one in which the victim’s feet (or any portion of their lower body) is in direct contact with the ground.
To many, this defies belief. How could a person die from hanging if all they have to do is stand up? You’re not alone. It was quite a shock to me on my first case as well, but the history is well documented. The images in this post are from a French text book entitled La Pendaison, La Strangulation, La Suffocation, La Submersion by P. Brouardel and published in 1897. Death by hanging is not dependent on full suspension. Any ligature that constricts airflow or blood flow can lead to death.
In fact, if I were to find someone fully suspended in a home I would be a little suspicious. CSIs would certainly have to entertain the idea that the scene may have been staged (although the full suspension would not, in and of itself, support a finding of staging) and look for other evidence that seemed out of place. There are other clues that support or refute a finding of suicidal hanging but I’ll get into those in another post.
So if you’re writing a scene involving a hanging you don’t need to have the victim fully suspended. In fact, it might seem a little suspicious to an experienced investigator. Partial suspensions are much more common. They do defy common sense though, so you can use that in your character development. Whether a defense “expert”, family member, or District Attorney, they may challenge your protagonist regarding the manner of death and leave your reader wondering until the very end.
Human vs “Animal” Remains
Police in rural areas get a lot of calls from hikers, hunters, and nature lovers who inadvertently stumble across bones in the course of their activities. Sometimes, the person’s dog may bring a strange bone back to the house and deposit it on the back porch. I know a detective who actually found a homicide victim while he was elk hunting! However one discovers such bones it’s natural for people to suspect the remains might be human and call police. In North America the bones of bear paws are commonly mistaken for human bones (they are very similar in appearance). If the bones have been chewed on by various scavengers then the identification process can become even more complicated.
If you’re looking to get into a tiff with a forensic anthropologist go to a crime scene littered with bones and ask them if they are human or animal bones. If you’re really lucky they will just respond with a simple ”yes”. If you aren’t so lucky they may offer a dismissive glare followed by something like “Well, they’re not from a f***ing plant!” If your character is a natural born smart-ass like me they may ask the question just to get their blood pressure up. It’s a common mistake of terminology (especially among police) but one you’d be wise to avoid in your novel. It’s another one of those devil is in the details issues with your readers. The fact of the matter is that all “animals” (including humans) have bones. It doesn’t matter if they are from an elk, a blue jay, house cat, or a murder victim.
Human foot articulated
But non-human remains can be an effective tool for your plot development. It’s interesting really. A good forensic anthropologist can look at some bones from ten feet away and instantly recognize them as non-human. The average detective or CSI can’t tell the difference though and may call out numerous people to the scene assuming that the bones are human. In your novel you can use this confusion to your advantage. In one scenario you could have a home owner or other laymen who’s dog has brought back a human bone (or collection of human bones) and buried them on the property. If the home owner thinks they are from deer or elk they may not call police until something definitive like a skull shows up. By then the police may actually think that person was the killer. In another scenario you might have a ton of volunteer searchers mobilized over a bear paw who, in the searching process, trample over the ground and destroy evidence of the “real” homicide scene (i.e. shoe prints, tire tracks, etc left by the killer). However you choose to use non-human remains just be sure you don’t call them “animal”.
Suicide Notes: Fact & Fallacy
As many of you know I regularly contribute articles to the Crime Fiction Collective BLOG every other Tuesday. It’s a really great BLOG for mystery writers. Today I am discussing suicide notes and how you can use them as tools to create leads, false flags, and tension between characters. Suicide notes can tell you a great deal about the motivations of the person (or even the suspect if the scene has been staged) and, as writers, you can use that language to steer your readers in certain directions within the story. Check out the posting here.
Politically Correct Policing
Today I have a guest blog on the Jungle Red Writers Site regarding little issues that tend to annoy me in life. Anyone who knows me will tell you that I don’t do “politically correct”, especially when there’s a suspect at large. I’m not saying this is always good, but sometimes you just have to be blunt and call it like you see it no matter who get’s offended. Anyway, I think the perspective can be valuable to you as a writer in recognizing those little issues that can frustrate CSIs or cause tension between various characters. Check out the posting here.
Holy Jumping Maggots!!
- The Cheese-skipper fly Piophila casei
This is one of those posts that is very focused but may be good for a laugh or squirm for your readers. I have written previous posts on forensic entomologists and the role of insect development in death scenes but this posting is about a particular behavior of a particular fly larvae. This species is commonly referred to as the Skipper Fly or Cheese-Skipper fly (Piophila casei) from the Family Piophilidae. This is a relatively small group of flies (about 70 species) found commonly in cooler temperate regions of the Northern Hemisphere (although they can be found anywhere). In non-forensic settings they can be associated with stored products like cheese (hence the name). In forensic cases they are more common in the later stages of decomposition when the body is drying out.
The particular behavior I am interested in is this larvae escape mechanism. When these larvae are disturbed they do the coolest thing. They fold their body in half and by rapidly flexing their body they propel themselves through the air. It’s quite a site to see a body infested with multiple maggots “jumping” all around. Watch the video below to get an idea of what this might look like. These little guys can propel themselves several feet away from the body. You can probably see where this is going.
I had a colleague of mine squirm and almost scream as one of these little guys launched into her hair while examining a body. It’s kind of a hazard of the job we all come to expect but when you consider where they’ve been crawling it can soften the knees of the most hardened professional. God forbid one launches into your mouth! If you are writing a scene with a body in the advanced stages of decay in a cooler climate you might consider adding this little character actor for the desired effect. It’s a tiny thing but your reader will appreciate your attention to detail and added depth to the scene.
