Category Archives: The Autopsy
Introducing the M-Vac DNA Vacuum
I love introducing you to cutting edge technologies that may turn your reader’s heads and make them turn the page. Forensics has never been a stagnant science. Dozens of researchers are pushing envelopes and making the imaginable come to fruition. One such device is the M-Vac. This recent addition to the CSI tool kit may revolutionize how we search for evidence and recover DNA that was previously unrecoverable. Vacuums are nothing new to the collection of trace evidence. I need to write a post on the history of the trace evidence vacuum which was introduced at early as the 1930′s. The M-Vac is the next generation trace evidence vacuum designed specifically for DNA collection.
Forensic scientists have made great progress in the collection, analysis, and turn around time of DNA testing in the last decade. The M-Vac uses a wet-vacuum method to release stubborn cells from evidence like clothing, textured pistol grips, and other surfaces where the samples may be hard to get at with swabs. It uses a DNA-free buffer solution that is applied and then recovered in one step through the application wand. The solution carrying the DNA samples is then deposited in a sterile collection bottle that can be tested for DNA profiles. The wand allows the CSIs to cover large areas and get into nooks and crannies that prove too difficult for swabs. Validation studies have indicated that the M-Vac collects 39 times more DNA than swabbing!
I’ve included a short video below that demonstrates some collection methods. One sampling procedure that wasn’t covered was the autopsy. I’m not sure what possible roadblocks may exist (if any) but it seems to me that this sampling method may prove very valuable in sampling certain areas of the victim’s body. Imagine sampling the neck in a strangulation case, genitals or breasts in a sexual assault, the wrists or ankles in a body dump where the victim was dragged, or even the victim’s hair. You may also get results from the outsole of a shoe used in a stomping or the hood of a vehicle in a hit and run. As the video indicates, this tech may open up new leads in cold cases as well. The possibilities are pretty endless it seems.
If your next novel deals with DNA evidence you might consider using a device like this. I suspect there are a number of CSIs and detectives who may be unaware of this technology. Imagine their surprise at reading about it in your novel.
What the Heck is Entomotoxicology?
The House fly
I’ve written before about the role of the forensic entomologist in death investigations. These professionals can provide critical information regarding the time since colonization and postmortem processes. One aspect of their analysis that is being utilized for frequently is the use of insects (like maggots) to screen for the presence of drugs or toxins (like Malathion). Before I get into the process, let’s discuss why this type of testing might be undertaken. Obviously, the presence of illicit drugs like cocaine, heroine, MDMA, or amphetamines, may provide critical information about a possible cause of death, criminal activity, and victimology. In the same light, the presence of prescription drugs may also shed light on the victim and their physical or mental health. Likewise, the absence of certain drugs may also reveal important clues surrounding the victim’s state of health. Did they need the medication to maintain a certain quality of life or health status?
Why not just review their medical records? First, the victim may not have a complete documented medical history. Some people gain access to prescription drugs through illegal or unethical means. Family members (even spouses or parents) may be unaware of certain health conditions. Additionally, the victim may not be identified at the crime scene. Insects like maggots can removes significant biomass during the decomposition process and some victim’s don’t have any identification on them. We may be able to extract DNA but that will be of little help if their profile is not on file. We may be able to construct certain features or details about their lives based on their physical possessions (clothing size, piercings, tattoos, etc.) but the presence of certain drugs or toxins may provide that extra clue that helps to narrow down missing person profiles.
The concept of using insects for drug screening is pretty straight forward. While the victim’s tissues and fluids (blood, urine) degrade through decomposition; the larvae do not. In effect, they act as mini-reservoirs. Eventually they will undergo some kind of metamorphosis but if they are found on a body they can be tested. As adults they tend to eliminate the toxins rather quickly but even trace amounts of some drugs have been found in recently emerged adult flies. Some research has even detected drugs in beetle frass (excrement) and fly puparia years after death. Testing is begun by crushing or grinding the insect samples in something like a mortar and pestle. There are a number of different tests that can then be performed including Gas Chromatography / Mass Spectrometry (GC/MS), Fourier Transform Infrared Spectroscopy (FTIR), and radioimmunoassay (RIA). In many ways the testing sample is treated like any other biological tissue. The effects of various drugs and toxins on the rate of biological development (of the larvae) is not fully known. These types of exams primarily screen for the presence or absence of drugs and toxins. The effects of such substances on insect biology is another matter the entomologist must consider when estimating the postmortem interval.
As authors you may consider using insects as a testing source for drugs or toxins, especially when other tissues are not viable. Consider too the absence of certain prescribed drugs that may affect the victim’s behavior or general health. The drugs may be illegal or they may have been stolen by the suspect from another family member, friend, or co-worker. The presence or absence of drugs or toxins may also reveal a “unique” data point in the unidentified victim’s profile to compare against missing person’s records, medical records, or even criminal modus operandi (such as the use of a date rape drug or poisoning by mercury). You probably already have an interesting application of drugs or toxins in your storyline. The use of insects to test for those substances will provide for some interesting dialog between characters or plot twists for your readers.
Back Spatter from Gunshot Injuries
Back spatter can also travel down the barrel!
There are basically two types of blood spatter; forward and back. Notice I didn’t say “splatter“. Blood spatter is caused when an object impacts a body and forces the blood to break up into smaller droplets. The majority of these droplets are then projected either forward (with direction of force) or backward (opposite the direction of force) essentially. Generally speaking, there is more forward spatter than back spatter in an incident and the blood will disperse in a “cone effect”. The amount of back spatter is dependent on both the energy of the impact and the amount of blood already present at the impact site. For example, a gunshot can create back spatter even when there is no preceding injury. This is influenced by other factors too though. Clothing can “trap” much of the back spatter depending on the type and layers of clothing and location of the wound. If the wound area is not covered with clothing (like the head) then you can see more back spatter. CSIs commonly see some degree of back spatter on the shooting hand in gunshot suicides with head wounds.
The degree of back spatter on the subject varies wildly though. A number of factors influence the deposition of the blood such as subject and victim body positions, wound position relative to subject, distance between subject and wound, the amount of energy causing the spatter, intervening objects (like shooting through a window), and the presence or absence of blood at the impact site just to name a few! The size of the resulting blood droplets varies too. Gunshots and explosions can produce very tiny droplets (with a diameter of 1mm or less) while other impact events can produce larger droplets from 2mm up to 10mm and even larger. You may find back spatter on hands, faces, ears, hair, clothing, weapons, furniture, or practically anywhere near the impact event. It can even be found on items that have been moved to another room (as in a staging). With gunshots, you may find spatter up to four feet from the impact site. In theory, you could find them even further away if there is sufficient air current such as high wind or even the close proximity of a fan.
So how would you use this in a novel? Back spatter can be washed from hands and clothing or even the victim (think of a dog or cat licking the victim). Tiny spatter is very difficult to see however. You could easily have a detective, spouse, or dry cleaner find these tiny spots on a garment, vehicle seat, or window blinds. If on clothing, consider putting the spatter on something like socks, undershirt, or underwear that would have been covered during the suspect’s version of events (or denial of events). That not only places them at the scene but could also place them in a state of undress at the time of blood loss. You get the picture. Be creative and use your imagination to produce a big plot twist.
Collecting Explosive Residues
I generally make it a point not to discuss certain aspects of bombing investigations such as the design of improvised explosive devices, formulas, detection capabilities, tactics, or render safe procedures. I avoid these topics to keep my colleagues safe and the terrorists in the dark. However, I can tell you a little about how we collect evidence from such events. We refer to them as post blast investigations and they can be very complex. As such, I’ll limit the discussion to some of the more obvious and common techniques. Not all CSIs are trained in post blast investigations so keep that in mind when you are developing your character. Agencies that deal with terrorism regularly, like the FBI, IDF (Revidim), Metropolitan Police, RCMP and many others, are more likely to have post blast investigators as opposed to small local municipal police agencies. However, in the United States, many sheriff and larger police agencies have bomb squads and post blast investigators thanks to the efforts of the FBI.
Now there are a number of ways to build a bomb and just as many different types of explosives but they all have one thing in common. They all go boom (unless the good guys take care of it first that is). The spot at which the device detonates is called the seat of the explosion. Contrary to what you may have read an explosion doesn’t typically destroy all of the evidence. It may damage and disperse the components over long distances but good investigators can always find something. So to keep this embarrassingly simple let’s think of evidence recovery from three different sources.
The first is the actual seat of the explosion. With large ground based devices this is typically represented by a crater. The larger the device the larger the crater (usually). Large vehicle bombs can leave a crater the size of a house while something like a briefcase may leave a much smaller crater. It’s not uncommon to find pieces of the device still in the crater. Of course, all of this is dependent on the type of explosive used. Regardless, traces of the explosive used will be found in the crater. Post blast investigators can take samples of the soil from the crater and seal it in air tight containers (to keep certain elements from escaping in gaseous form).
The second type of collection site is from surrounding surfaces like trees, buildings, vehicles, clothing, traffic signs, even victims at autopsy. You see, explosions can release a lot of energy. That energy creates a shock wave (much like that produced out of the muzzle of a gun when fired) which can carry explosive elements and depositing them onto surfaces as a residue. Think of it like soot from a fire. This video link will demonstrate the appearance of a shock wave following an explosion. Explosive Shock Wave Video. Investigators can sample this residue with everything from small cotton tipped swabs to larger cotton pads. The samples are also sealed in air tight containers to ensure the volatile compounds do not escape.
The last type of location is from components of the device. If you’ve ever read about notorious bombing scenes you know that parts of the device can be found many blocks from the seat of the explosion. It may be anything from pieces of a vehicle to small electrical circuit boards from the timer. These components were obviously in close proximity to the device and should have explosive residue on them (assuming they are collected before environmental degradation). If the items are small they can be placed in air tight containers. If they are larger (like a vehicle axle) they can be swabbed.
Obviously, I’ve left a lot out. I haven’t even touched on sensitivity of detection for obvious reasons. Bombing scenes can be very challenging and dangerous. It’s even worse in a war zone. But even in a war zone forensic evidence can be collected and analyzed. As with all crime scenes you just have to know where to look for evidence. In bombing scenes it can be almost anywhere. Rooftops, the sides of buildings, tree tops, even rain gutters ad sewers (following fire suppression efforts). There’s a ton more that goes into these investigations but that information is best kept secret.
The Autopsy Part 2: The Internal Exam
There has been a lot of interest in how autopsies are performed. Frankly, it’s not something most people experience (in life that is). So I thought it would be informative to give you a little peak behind the curtain and find out how these procedures take place. Consider this a brief summary as each case may require special procedures depending on the crime or suspected cause of death. I have already explained the external examination. Now it is time to discuss the next phase, the internal examination. You might think that all autopsies include an internal examination but in my experience the final call is made by the coroner or medical examiner. Personally, I think every suspicious death autopsy should include an internal exam and most do but, occasionally the coroner may issue a death certificate based solely on the external examination. This may include cases of motor vehicle accidents, suicide, or natural deaths such as a patient dying after a long documented battle with a terminal disease.
The purpose of the internal examination is to fully explore all potential causes of death. Forensic pathologists are concerned with more than just criminal acts resulting in death. They also have an interest in public health and personal medical conditions that may affect the victim’s family members (like a hereditary disease). Likewise, a patient suffering from a terminal disease may die prematurely from improper care or negligence and sometimes the internal examination is the only way to uncover that evidence.
The internal examination begins with what we refer to as the “Y” incision. This is a dissection technique to gain access to the internal organs of the torso. Incisions are made from each shoulder to the sternum and then straight down to the groin. The skin is then reflected (cut) back and the ribs are cut along the sides and the “plate” is then removed to expose the organ area. Each organ is removed, weighed, photographed, and dissected by the pathologist. Small portions of each organ will be preserved for future study and tissue samples will also be collected for histological examination. They are looking for injuries, evidence of disease, as well as the general health of the organ. Pathologists will examine and collect the stomach contents which may reveal last meal evidence or prescription drugs (in cases of drug overdose). All along the way they will be documenting their findings in notes, charts, photographs, and occasionally video.
Then they open the cranium. The pathologist begins by cutting the scalp around the back of the head and then reflecting (peeling) the scalp up over the head to the top of the eyes and on the back side down to the bottom of the skull. This exposes a majority of the cranium. A bone saw is then used to cut through the bone and pull the skull cap off exposing the brain. The bone saw can generate some bone dust and an interesting musty smell so I generally make sure I’m on the other side of the room. The brain is covered in a thin white sheet or film called the dura that resembles an opaque saran wrap (bad analogy but appropriate for non-scientists) that has to be removed before you can access the brain. Once the dura is removed, the brain is removed and examined like the other organs. It may even be sectioned (cut into thin slices) to look for certain pathologies. The pathologist will also be looking for fractures or bruising to the cranium and scalp (as might be found in blunt force trauma). Following the examination of the brain the pathologist will examine the throat. Depending on the circumstances surrounding the death they may be looking for anything from an obstruction (choking) to soot (fire). Of course the mouth will be examined for injury as well. This could include missing teeth, bleeding, bruising, etc.
Black soot in victim’s airway
As I’ve mentioned, each autopsy may require examination and procedures not mentioned here. The order of the examinations (Trunk, head, throat, etc.) may also vary from pathologist to pathologist and the circumstances of the death. Most autopsies are completed in under two hours. Some can take a bit longer if there is extensive trauma to document (like 37 stab wounds). Although the physical procedure is relatively short it may take days or weeks to get all of the toxicology and histology results back (even if done in house) because of backlog. If the victim has evidence of prior injury (like healing fractures, bruising, or evidence of prior surgery) the pathologist will document it and assess if it played a role (contributed) to death. Every medical examiner has different rules as to who may attend the autopsy in person. Some are extremely restrictive (only the pathology staff and one member from the crime lab) others seem to allow anyone to attend. I’ve been in some with a dozen or more people crowding around and that can cause it’s own challenges. As far as evidence retention, the pathologist will take custody of all biological evidence. If there were something inside the body like a bullet, knife tip, or other trace evidence, the crime lab would typically take custody of it.
Today pathologists must physically dissect the body but there may come a day when much of this work is done in what some call a virtual autopsy. You’ll probably never get away from physical sampling but fifty years from now the autopsy procedure may look very different. Watch the below video for a hint at how these procedures may develop. I think if nothing else, the virtual autopsy may be a preferable method for presenting images in court.
As writers you may not want to get too deep into the weeds on autopsy procedure but, it is helpful to understand it. Autopsies are hard for some folks to deal with and some investigators and DAs would prefer not to be there. It’s easy to understand why. It is one thing to see a dead body. It is something else entirely to see one subjected to this procedure. Pathologists exhibit an enormous amount of care when performing these procedures. There is a decorum of professionalism and they don’t tolerate clowning around. It is a very serious event. Having said that it is also a place where emotions can rage inside each individual. Your characters may ride a wave from sorrow to anger and back again before the procedure is completed. Think about how each character might react to the details as they emerge during this procedure and use that to give the reader a little insight to their thought process.
Covering Bodies at Autopsy
I see this a lot on television and it really cracks me up. The detective comes into the autopsy suite and the victim’s genitalia or breasts are either covered with a small cloth or obscured by a bright spotlight. I understand why producers can’t show nudity on the major networks in the United States but I wonder if authors believe we actually cover up dead people’s genitalia at autopsy. The short answer is no. Dead people can’t get embarrassed. Detectives, CSIs, and pathologists are used to seeing naked dead people too; much worse actually. You can’t really avoid it while investigating death. In fact, every autopsy should include an examination of the genitalia including photography. Primarily this is to check for injury or disease that may be related to the cause of death or associated with a crime. We also have to search these areas for evidence like DNA, hairs, and fibers. It may be counter-productive to place a towel over a woman’s breasts if you need to swab them for touch DNA.
I’ve talked previously about the problems associated with covering dead bodies at crime scenes. Sometimes a cop or firefighter will cover a body because they don’t want the body visible to the family or public. This is especially true with bodies discovered in public places. We don’t encourage it but if your body is in the driveway of a house in front of a school bus stop (this happened to me) then you generally cut the cops a little slack. But these concerns don’t exist at autopsy. In fact, one of the first things we do at autopsy is remove the victim’s clothing.
A lot of authors have asked me about the circumstances in which we will collect sexual assault evidence. The truth is we collect samples in many cases which may not seem necessary. Most of the time we do it just to cover our bases. You only get one chance to get the evidence and the time and effort is inexpensive compared to an exhumation. Think of a traffic accident involving a teenage girl. Why might you search for sex assault evidence in such a case? What if the reason for her erratic driving was because she had been raped at a party before the crash? What looks like a tragic accident may have much deeper implications. CSIs always have to consider the improbable if we ever hope to discover it.
So if you are writing an autopsy scene make sure you don’t cover the body. Detectives, pathologists, CSIs, and attorneys are all professionals and we see naked people all the time. It comes with the territory.
The Autopsy Part I: External Examination
I can’t believe I haven’t written about this yet. Most of you have probably never been to an autopsy and while words alone can not provide the true flavor of the experience I think it may help to briefly explain the process. Coroners and Medical examiners usually perform an autopsy for any suspicious or unattended death. In the United States they do not need the permission from any person or entity to perform the autopsy. Most pathologists will be sensitive to certain religious or cultural protocols but they are not legally bound to adhere to them. One reason the medical examiner can perform and autopsy over the protest of the family is that family members may be suspects. Imagine how easy it would be to commit a murder if, as the spouse, you could prohibit the medical investigation into your wife’s death. That could be a real recipe for disaster.
In the United States we have a mixed system of Coroner and Medical Examiner offices. Most of these jurisdictions are defined by counties and major cities. Some may even be defined by judicial districts. Some rural states don’t have forensic pathologist and may have to drive a body to another state for an autopsy to be performed. Once the body arrives at the coroner’s office, the procedures may vary from case to case and office to office. Some pathologists want the body left sealed in the body bag until they begin the autopsy. This procedure may also happen with bodies sealed with an evidence seal in homicides. Other times an attendant or investigator may fingerprint the body prior to autopsy. They may also take x-rays and log in personal effects from the victim’s clothing. X-rays may show anything from foreign objects (choking), surgical devices, bullets, or even knife tips. Before any incisions are performed however, an external examination has to occur.
The external examination typically begins with photographs. We take pictures of the clothing, any visible injuries, and especially the face. It’s important to photograph the body from different perspectives. This is our one chance to get the body photographed properly. If we forget to photograph something we may never get a chance to go back. Just concerning the head we will take pictures of the face, right side, left side, neck, top, and back of the head. We may then take close-up photographs of injuries, jewelry, needle marks, and any distinguishing marks like tattoos, moles, or birthmarks. Then we remove the clothing and take a new round of photographs. It’s important to photograph the body from all sides and perspectives. Some areas that may get over looked include the soles of the feet, inside of the mouth, and a close-up of the neck.
The next step is the collection of evidence. The clothing is pretty easy. Most of it may get cut off but you have to make sure you don’t cut through any damaged areas. We also look for trace evidence. If the hands are bagged we’ll open those and scrape fingernails for trace DNA. We’ll also look for hairs and fibers, some of which may fluoresce with an alternate light source. If the victim died from a gunshot wound we’ll also look for gunshot residue. If there is any suspicion of a sexual assault then we will collect a “rape kit“. Once all the evidence has been collected then the body is washed. Dried blood and dirt is cleaned off and if any injuries are more visible they are photographed again! Check back in a bit and we’ll discuss the internal examination.
What are Petechiae?
Have you ever wondered how medical examiners can tell a person was smothered/strangled (asphyxia) if there is no ligature or damage to the neck? Although not 100% conclusive, the presence of petechiae can support such a finding. Figuring out how a person died can be pretty tricky if there isn’t some obvious trauma like a gunshot or knife wound. This is especially true if the victim is found in an otherwise benign setting, like in bed. Imagine finding an older woman dead in her bed. Imagine further she was in poor health. Is it possible the police could simply think the woman died from natural causes or some illness? Are there clues, so tiny, that they may be missed during casual observation? This is the reality that no CSI or detective wants to face and why autopsies are so commonly performed. Petechiae, also referred to as Petechial Hemorrhaging, are small pinpoint locations of bleeding where blood vessels have ruptured. They are most commonly seen in the eyes (and eyelids) but can also be found in the face, neck, and upper chest.
Sometimes they can be hard to spot. They are most easily seen against the white of the eye, but a trained forensic pathologist can easily spot them in other areas of the body as well. They can even be found on internal organs. These pin pricks occur when there is increased venous blood pressure. This is what commonly happens during asphyxiation. When a person’s airflow is cut off or restricted (smothering, suffocation, strangulation) the body struggles to breathe and move oxygenated blood to the vital organs. This increased pressure can be too much for the blood vessels and they simply burst open. Now this condition can also be seen in non-criminal deaths like drownings and certain heart failures so the presence of petechiae isn’t 100% conclusive for strangulation or smothering.
But if you are writing a scene in which a person dies (or is suspected of dying) from asphyxiation then you should consider mentioning petechiae. Of course, if the scene has been staged to look like a suffocation (such as placing a plastic bag over their head) but there is no petechiae then your detective characters should make note of the lack of petechiae. Petechiae is also very difficult to see in advanced stages of decomposition. In such cases the medical examiner may have to look for other evidence that might indicate strangulation such as ligatures. You could write a scene in which the petechiae are overlooked by a small town Coroner or inexperienced police investigator only to be discovered later by the state Medical Examiner. Of course, by that time the suspect may have had time to flee the area or get rid of incriminating evidence leaving your detective back at the drawing board. You could even have the victim’s body cremated and then your detective spots the petechiae in a photograph or from a notation in a report that describes a “rash”. Without the body it would only be speculation but it might cause your detective to suspect foul play where none existed before. The options are almost endless so have fun experimenting with different scenarios.
Searching for Trace Evidence Part 3: The Victim
I have written previously on the search for trace evidence from the crime scene and suspect and now it is time to talk about the victim. CSIs search for trace evidence because it serves as a powerful tool to link a suspect, victim, and crime scene together. Many violent confrontations between victim and suspect will result in an exchange of trace evidence. Victims may also retain trace evidence from a crime scene or secondary location. Whether alive or dead there are certain areas that may yield valuable evidence depending on the type of crime and actions of the suspect. trace evidence is generally collected by either swabbing, forceps, or adhesive lifters. Here are a few places CSIs routinely search for trace evidence on the victim.
Hands:
- Suspect DNA may be found under the victim’s fingernails. Scraping or cutting the nails are the preferred methods for evidence collection.
- Suspect hairs or fibers may also be caught up in jewelry like watches and rings, especially if there was a struggle. Hairs may also be found in the clenched hands of a deceased victim.
- “Touch” DNA may also be found on the victim’s hands, especially if the victim had significant contact with the suspect’s skin during a struggle.
- These locations may also contain soil, fibers, pet hair, or vegetation from one or more crime scenes.
Fluorescent markings
- Broken Fingernail
Hair:
- Victim hair (head and pubic) can easily retain everything from suspect hairs, vegetation, carpet fibers and the like helping to link the suspect, vehicle, or crime scene.
Mouth:
- Victims may sometimes bite the suspect and in the process skin or DNA can be transferred or retained in the teeth or on the lips. In some cases foreign objects like fabric gags, tape residue, even gravel may be found.
Genitalia & Breasts:
- Genitalia may be an excellent reservoir for trace evidence including semen, even after a victim has showered or bathed. Body cavities are generally swabbed to recover DNA but examiners should also consider that foreign objects like knife tips, vegetation, or other items may also be found.
- In some sexual assaults a female breasts may contains suspect DNA which can be swabbed.
Clothing:
- Victim’s clothing can hold trace evidence just like suspect clothing. Shoe tread can retain dirt, vegetation, hairs/fibers, even blood. Velcro straps on shoes (or anywhere else) can also be a great trap for trace evidence.
- Pant cuffs and pockets are also great locations to search.
Other Locations:
- Stomach contents. I’ll be writing a specific post soon on stomach contents but suffice it say, sometimes victims ingest things during a struggle which can include suspect body parts or foreign objects.
- Ears and nostrils may sometimes contain hairs, fibers, even soil or vegetation from a crime scene.
- Maggot masses. This is an often overlooked location. When medical examiners or entomologists scoop up large samples (or individuals) of insects they may also inadvertently be collecting hairs or fibers clinging to the insects as they crawl across the body.
