Category Archives: The Crime Scene
So most of you know that in addition to writing novels I also continue to conduct research in the forensic science. Some of it is probably quite boring but I thought you might find my latest paper interesting. We wanted to see how long after deposition we could detect blood on concrete. Concrete has spread across our world at an exponential rate and to no one’s surprise, CSIs must search it frequently for evidence. Blood is generally considered to be fragile and may “disappear” from sight after a few days. We’d like to get called to a crime scene immediately but that doesn’t always happen. A previous study had found bloodstains outside on a concrete wall about two months after deposition but we thought it may be possible to detect it much later.
We also wanted to test the effects on a completely exposed surface (to the elements) with the possibility of some foot traffic. I suspect that we could detect even older blood in a garage, warehouse, or basement floor. We decided to use the blood reagent Luminol because of its sensitivity to blood (1:1,000,000). Luminol is a chemiluminescent reagent that has a long history of use in forensic investigations. Here is a link to the paper if you want to read it (or need to fall asleep!).
As crime novelists I thought it might give you some ideas for a realistic scene. The technique could be used in any scene where blood may have been deposited. Some examples for your novel could include traffic accidents, drive-by shootings, or any other type of violent crime. DNA analysis would not be possible but your detective or CSI might be able to verify a statement from a witness, co-conspirator, or even a psychic! While our study used an “X” type pattern it is plausible that one may uncover footwear or tire impressions or other bloodstain patterns (like drag marks). It may be a great way to keep your reader engaged in the scene as they “discover” the evidence alongside your characters.
I have been a bit AWOL lately. Every now and then I need a vacation and this last one turned out to be quite a little adventure. So today I thought it would be interesting to talk about the next generation of crime scene mapping. When I first started crime scene work we used metal tape measures and did our crime scene sketching on large pads of paper. While paper isn’t obsolete, the next generation of crime scene mapping offers many advantages. Tape measures are a pain in the butt. They bend, they come loose, and sooner or later you drag one through a pool of blood (yuck!).
Over the years CSIs have been utilizing various laser based measurement devices. They vary from small hand held range finders (great for inside measurements) to Total stations (like the ones you see surveyors using). Near the top of that list is the automated laser based scanner. These types of units gained international exposure during the reconstruction of the car accident claiming the life of Princess Diana. These units are not in common use yet due to the cost (some in excess of $100,000.00) but more and more agencies are beginning to use them.
The above video demonstrates one such unit from Leica instruments. I’ve used a number of Leica products and found them to be top notch. The scanner is about the size of a small trash can and mounted atop a surveyors tripod. Once activated the unit will bombard the crime scene area (up to a distance of nearly 1000 feet) with millions of laser pulses which bounce off various surfaces and return to the unit. It will scan a full 360 degrees and 270 degrees above and below the unit. Basically everywhere except the unit location. A typical room can be scanned in a few minutes. CSIs can also link the unit with GPS which is really handy in outdoor crime scenes (especially ones in remote locations). The units can even operate in complete darkness.
Those millions of points create an exact three dimensional map of the scene that can be represented in a rotational diagram. It even records color. Utilizing the scanner software this virtual map allows CSIs to determine distances between any objects in the scene. No more missed measurements and the accuracy is phenomenal. The CSI can also zoom and pan around the image to view evidence from different perspectives. As you can see in the video, certain points can be hyper-linked to crime scene photographs or even text reports. This is a powerful tool for the reconstructionist and can be useful for prosecutors as well.
This is cutting edge stuff and you may want to consider using this technology in your next novel. Remember, this unit will record everything visible to the laser so it may even “find” a piece of evidence missed by your detective. Maybe your scene was mapped at night (dumped body or car accident) and a crucial piece of evidence wasn’t seen by the on scene responders. Then your protagonist can go back and find the crucial clue. Use your imagination and have fun with it!
Today I’ve been invited to share a post at Writing With the Top Down BLOG on this method of determining the three dimensional area of origin in bloodstain pattern analysis. I’d love it if you could stop by and take a look.
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.
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.
I love being out in the woods. I don’t mind walking established trails but it takes no convincing to get me “off trail”. One of the reasons I love getting off the beaten path is that I get to see things most people don’t. Wild critters, small brooks, or hidden canyons. I sit and wonder how long it has been since another person was seeing what I’m seeing.Most of the time I’m not that far away from the rest of those enjoying the outdoors. Maybe just over a hill or around a bend but, it makes all the difference in the experience. I often think “wow”, I would have never seen that bear, bobcat, or elk if I hadn’t come this way.
In the modern world we’re conditioned to follow certain paths. Sidewalks, roads, green belts, subways, etc. Think about it…don’t you take the same path to work everyday? What about the grocerie store, gas station, or your child’s school? Partly this is because we’ve determined the easiest, most efficient, route. But even when you’re going somewhere new you generally stay on some kind of path right? Don’t most of you hesitate to cross open space unless there is a trail? Even then, if there is a sign prohibiting it, most people won’t. This type of thinking limits the world we see and experience. Criminals aren’t restrained by thinking.
One of the toughest things to learn as a new CSI is to stop thinking like everyone else and start thinking like a criminal. You have to divorce yourself from even the most basic and accepted thoughts. Criminals have to conduct their “business” and get from point A to point B but, some of them don’t want to draw attention to themselves (just like animals). At least the successful ones don’t. They like to conduct their business in the “shadows” or “off the beaten path”. There is a whole world of activity going on right now…off that beaten path. These are worlds within worlds and it is the job of the CSI to find them (at least as they pertain to criminal activity).
These are places where most of us have no reason to go. Culverts, abandoned buildings, tunnels, and over grown gulches. Sometimes these places are right under our noses. I remember being a young officer and getting a call about a “satanic” alter being found at a movie theater. Turns out there was a “hidden” room above the concession stand but below the projector room. In the old days they used the room to cut film reels. It hadn’t been used in decades for that reason but someone was using it now. There was no way to tell how long it had been in use but that’s not my point. The point is that the activities were going on right under everyone’s noses because no one ever had reason to go in there. The room was “off limits”.
Don’t forget about these “hidden worlds” in your writing. I’ve made it a point in my novels to include such places and I think it adds a powerful layer of mystery to the settings. These places are even more frightening when your characters stumble upon them for the first time. It may be a detective, teenage runaway, or concerned parent. The possibilities are endless and can be driven by the structure itself. The video below is apparently from an old missile silo. Imagine the types of crimes that could be going on in such a place and how hard it would be for someone to stumble upon it? Might be a good idea for a novel eh?
Real life CSIs sometimes have to find innovative ways to capture evidence. There are a ton of commercial products available for nearly every type of evidence but Murphy has a tendency to rear his ugly head at the most inopportune times (like a homicide scene). Cameras break, your partner forgot to re-stock supplies, or you simply run out. In most cases you can’t just run down to the local Walmart and pick up exactly what you need. Good CSIs learn to develop alternative methods of collecting and preserving evidence (if possible) in the event you need to have a fall back plan. Some purists may scoff at such an idea but in my opinion it’s better to have something collected than nothing collected. The need to use unconventional collection methods is probably more likely for your private detective or amateur detective character. These folks may not have an impressive array of CSI gear because they don’t have to concern themselves with those matters often.
I’ve noted before that footwear evidence is one of the most commonly overlooked categories of physical evidence at a crime scene. Some of that is due to a lack of training, lack of awareness, or simply not having the proper equipment. In real life, the crime lab isn’t called to every crime scene. Usually we just go to the major scenes. Patrol officers don’t carry around electro-static dust print lifters, alternate light sources, and other specialized equipment so sometimes footwear evidence gets overlooked. One of the better surfaces to find two dimensional footwear impressions at crime scenes is paper. Paper may get scattered on the floor during a ransacking or it may just be trash on the floor (like in a warehouse). You can even find these dust prints on broken drywall, carpeting, or doors that have been kicked. Either way it can hold valuable clues. These impressions can be latent (invisible) and need some degree of processing to make visible again.
So what is your amateur detective to do when he/she spots a sheet of paper at the crime scene and thinks there’s a footwear impression on it? One simple process is to use blue carbon paper to make a lift. For some reason, black carbon paper isn’t as good. The process is really quite easy. You start by taking the paper evidence and securing it to a hard flat surface. Taping the corners works well. Then you lay a sheet of blue carbon paper down over the area you think may hold the dust print. Cover that carbon sheet with a manilla file folder or pad of paper and use a 4″ rubber roller to “press” the dust print onto the blue carbon paper. Simply roll the rubber roller firmly back and forth over the area a few times to transfer the image.
Once that is done the detective can flip over the carbon paper and use a strong oblique light (like a flashlight) to see the image in a darkened room. Any windowless room (like a powder room) works well. Voila! The invisible shoe print is now visible. It may be possible to individualize an impression to a particular shoe but even knowing the make and model of the shoe can be helpful in an investigation. If your prime suspect only wears Nike and the shoe in question is a cowboy boot you may need to search for another suspect right? In the end, a professional CSI would probably get better results using a gel lifter or ESDL but keep this trick in mind when writing your scenes. If your “detective” is unprepared then this might be a good option to recover evidence others may have missed.
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.