Crime Scenes for Writers: DNA and Biologics

Here we are at the last post in the series. Time flies, right?

Most of us are familiar with DNA, the individual blueprint for each of us. DNA testing has come so incredibly far in the last twenty years, almost to the point that we expect DNA to answer most if not all of our questions. That makes CAN an interesting place for writers to stymie the investigator (and the reader).

DNA is a powerful tool, yes, but not without exception in the field of criminal investigation. Consider the following scenario:

The Case of Sally Simms

Sally lives alone in her apartment. In the last three days, she’s had new appliances installed, new cable run for the internet, her boyfriend has visited several times, her sister and her sister’s boyfriend were over for dinner, and she had a coworker over for coffee.

Sally is found dead on the floor of her hallway. The science teams go through her apartment collecting everything they can find and Sally goes off to the autopsy table. The police begin with the list of possible suspects: Sally’s boyfriend, sister, sister’s boyfriend, the appliance installer, the cable installer, and the coworker.

DNA is everywhere. Each person in the apartment left their DNA behind. If Sally’s cause of death was a blow to the head, DNA is not helpful unless the object is found and DNA is recovered from parts of the object only the killer would have touched. Your police detective must turn to other investigative means.

During autopsy, should DNA from seminal fluid be found to match both the boyfriend and the sister’s boyfriend, Sally’s sister is going to want an explanation, but it doesn’t make either of them the killer, especially as Sally was dressed and in the hallway. Scrapings from under Sally’s fingernails might yield DNA, but if the suspect shows a scratch healed beyond the time frame of her murder, it might just mean Sally didn’t scrub her hands or under her nails.

Plausible DNA

Now, in most cases, DNA is eliminated because it has a plausible reason for being where it is. If other lines of investigation develop a suspect, DNA might support it, but not be conclusive. I don’t know about you, but I get a perverse kick out of writing crime stories in which DNA is not a major part of evidence, just because I can and I like the unexpected.

DNA is absolutely helpful in the case of serial crimes such as rape and murder, since unknown DNA from crime scenes is entered into and checked against CODIS, the Combined DNA Index. Once a suspect’s DNA is available for match, he or she could be connected to a series of crimes.

DNA can be collected from almost any surface and from almost any body fluid. Hair won’t give DNA but the hair root (if torn out) can. Naturally shed skin won’t give you much, but scrape your arm across an abrasive surface and it’s possible.  And when stranger DNA is present from a person who has no explanation for being at the location, good chances are you have your criminal.

Biologics

But there’s more. In recent years, we’ve made serious headway into biologics which, in addition to DNA and fingerprints, also includes palm prints, palm vein patterns, facial recognition, ear recognition (mostly in Europe still), Iris patterns, retina recognition, hand geometry, and odor or scent.

What was partially developed for security has become a database of biometric information. The Department of Homeland Security has IDENT, which includes biometric and associated biographic information. The Department of Defense has ABIS, the Automated Biometric Information System. CODIS, which also includes the National DNA Index, will, I suspect, branch into biometrics if it hasn’t already.

We already use biometrics to solve a crime such as Sally’s. Even if the killer wore gloves, should a lamp base or makeshift weapon turn up in good condition, it would be possible to match the size and shape of the hand to the person who wielded it. If her building has solid security camera coverage, facial recognition might identify or confirm a suspect entering and leaving the building near the time of the murder.

The Future is (Mostly) Now

The possibilities are as numerous as the writer’s imagined scenarios.  Consider shifting the story ten years into the future, and the writer could have a lot of fun with solving Sally’s murder.

I hope this series has been helpful. I’ve been working on a series titled Body of Evidence, but I’m not certain you would be interested in reading about the evidence a body can yield after death. Please comment below if you’d like me to post the Body of Evidence series. Though it’s not written in graphic language, some of the subject matter may prove uncomfortable for some readers.


Has anything in this series changed the way you look at criminal investigation from a storyteller’s point of view?

Other posts in this series:

Crime Scenes for Writers: Introduction

Crime Scenes for Writers: Reading the Scene

Crime Scenes for Writers: Fingerprints

Crime Scenes for Writers: Blood Evidence

Crime Scenes for Writers: Ballistics

Crime Scenes for Writers: Trace

Crime Scenes for Writers: DNA and  Biologics

Crime Scenes for Writers: Trace Evidence

Using trace evidence to solve the crime in your story is a great way to delay the payoff and finger the guilty party. I’ve given a list of the most common types of trace evidence and a brief description of each, though they could all be a post on their own.

Fiber

Clothing, leather, car interiors, carpet, and rope can all provide fibers for the investigators to discover and trace. The Mass Spectrometer is one tool used to identify the chemical makeup of a fiber. For example, carpet manufacturers’ and some fabric manufacturers’ product chemical signatures are in a database or researchable. This could narrow down the year, make, and model in the case of a car, or distribution information in the case of carpet and other fibers.  The most common use of fibers, however, is to match them from the crime scene to the suspect or the suspect’s environment.

Plant

Plants have DNA just like we do, so seeds or pods can often be linked to a specific plant. This might tell investigators where the suspect or the victim spent time as plants are often geographically specific.  Another use would be, for example, the discovery of seed pods in the suspect’s vehicle and matching them to the seed pods under the victim.

Insect

Larvae and living insects aren’t considered trace evidence, but webs, egg casings, insect parts, and evidence of bites or stings can yield evidence as to location, length of time the victim was at the dump site or crime scene, and even season if the crime occurred well before discover.

Hair

Humans and animals shed hair all the time, making hair one of the most common types of trace evidence. Once a suspect is identified, strands of hair can be matched. If the hair is pulled from the root, it may contain enough biological material to get a DNA sample. Pet hair found on or near the victim and also in the suspect’s environment (matched to a specific animal) can also boost the prosecutor’s case.

Fluids

Fluids include bodily secretions, of course, but other fluids include tree sap, cleaning products, chemicals, beverages, oil and gas, and water (pond water, ocean water, etc.). While these give information about the crime, I’ve always thought it would be interesting to use a fluid as the breakthrough piece of evidence. Something totally out of place would stump investigators and extend the tension of the story.

Particulates

I like this sort of evidence, and I’m intrigued about how to use particulates to good effect in a murder mystery. Here are four:

  • Paint: In addition to binding chemicals, paint often includes a mineral or metal as a color ingredient. These can be matched to known paint products, vehicles, and other elements of locations. In the world of crime shows, I’ve seen it most often used to identify a vehicle, but wouldn’t it be fun to connect it to an artist’s studio or the statue in the town square?
  • Soil: The great thing about soil is that it’s fairly localized depending on the particulates. Sandy, clay-based, loam, fertilized, mineral-rich . . . all give the investigators information they might not otherwise discover.
  • Metals: Paint, vehicles, tools, clothing fasteners, soil, weapons, and much more, contain metals that can be traced and/or matched to the crime scene, dump site, or suspect’s environment. We see it used most often to identify, again, a vehicle, but flecks of gold might indicate a manufacturing process, and copper shavings might point to the plumbing or construction industry.

Trace evidence offers so many opportunities for the writer and suspense for the reader. It’s by far my favorite type of evidence to include in stories.

The last post in the series is DNA and Biologics. See you then!


How many ways can you think of to stump the reader and detective with trace evidence?

 

Other posts in this series:

Crime Scenes for Writers: Introduction

Crime Scenes for Writers: Reading the Scene

Crime Scenes for Writers: Fingerprints

Crime Scenes for Writers: Blood Evidence

Crime Scenes for Writers: Ballistics

Crime Scenes for Writers: Trace

Crime Scenes for Writers: DNA and  Biologics

Stay Limber

Yolen Quote TSM

Just like athletes, musicians, and performers, writing improves with practice. Often, writing improves ONLY with practice. Are you practicing? Are you cultivating a writing practice? If so, you have seen for yourself how keeping your writing muscle limber has improved your prose.

Crime Scenes for Writers: Ballistics

muzzle-1080231_640Ballistics is one of the older forensic sciences. As far back as the early/mid 1800s, bullets could be matched to a particular caliber of weapon. However, it wasn’t until 1895, after rifling was introduced, that ballistics came into its own. Improvements in microscope photography and the introduction of the electron microscope in the 1970s brought the forensics of guns into the modern era.

However, there are two problems with using ballistic evidence. The first is that some bullets fragment on impact. Forensic scientists need enough fragments to reproduce an image of the bullet. If they don’t have them, the bullet is of little help. The second is that, in order to compare a bullet from a crime scene to a bullet from a particular gun, the lab people need the gun. No gun, no comparison, though the bullet may be matched to other crime scenes through NIBIN/IBIS (National Integrated Ballistic Information Network).

Guns, when recovered, can yield significant information including biologics and fingerprints. I’m guessing that’s why so many murder weapons end up buried or tossed into deep water.🙂

Other elements of investigation include the trajectory of the bullet, the velocity, if it can be determined, and the presence of gun powder residue, either on the suspect’s hands or near the victim’s wound (we’re already familiar with the term “stippling” from TV, which indicates the gun was in close proximity to the victim when fired.

Recovered suspected weapons are fired into a water tank. The bullet is removed from the tank and compared to any bullets or fragments found at the crime scene. Rifling marks, the lands and grooves, are individual to each gun. There may also be indicators of speed of rotation as the bullet passes through the barrel, and/or marks from the firing pin. Criminals who bench-load their own ammo probably leave tooling marks and individual elements in their gun powder as well.

I was happy to see a show this past year in which a detective explained to a gang member exactly why holding the gun sideways gangsta-style was a bad idea. The kid didn’t listen and the gun ejected the shell into his face. It brings to mind the fact that investigators can tell a lot about the gun and the position of the shooter by where the shell casings end up.

Speaking of shells, we’re also familiar with the term “policing the brass,” which indicates the shooter picked up his spent shells and took them with him. Most shooters don’t take the time, possibly leaving behind prints or other information with the casings themselves. I had some first-hand experience due to an unruly neighbor. My husband and I got a mini-lesson in trajectory and helped locate the casings. Each was picked up with care and stored in evidence. That’s why I own a revolver. (Just kidding . . . about the why, not the revolver.)

This doesn’t just refer to guns, but one thing TV routinely gets wrong is the use of plastic bags for evidence. Most evidence is collected in paper bags. Guns may be put into a paper bag or wrapped in brown paper. Paper preserves the evidence that plastic might easily destroy.

Several great sites exist for writers who want to know more about ballistics and guns in general to create accuracy in their stories. For examples, the NSSF published The Writer’s Guide to Firearms & Ammunition as a pdf download. But my favorite of all time and my go-to for questions is Lee Lofland at The Graveyard Shift. If you are at all interested in writing crime stories, his site should be your first bookmark.

Next week is trace evidence.


 

Do you find ballistics evidence an interesting part of the story or less so? If not your favorite, do you think it’s because we’re more familiar with it?

Other posts in this series:

Crime Scenes for Writers: Introduction

Crime Scenes for Writers: Reading the Scene

Crime Scenes for Writers: Fingerprints

Crime Scenes for Writers: Blood Evidence

Crime Scenes for Writers: Ballistics

Crime Scenes for Writers: Trace

Crime Scenes for Writers: DNA and  Biologics

Take Responsibility for Your Writing Life

Well. I’m a little red-faced today. The crime scene series will continue. As soon as I find it. Don’t worry, I have backups of backups. I just transferred everything to a new computer this week and apparently missed a few files. Embarrassing! And entirely my fault.

But it got me to thinking.

I like excuses. They seem to provide lubricant for slipping out of situations in which I am at fault. However, I try hard not to make excuses because, really, who cares? They don’t change the failure, right? They can’t undo a missing post, a lost opportunity, or a broken promise. Excuses might appease and reduce the fallout, but doesn’t let us own our mistakes and face them.

For that, we need to take responsibility.

As writers, aren’t excuses just easier?

  • I was too busy to write today.
  • The boss needed me so I couldn’t write.
  • The kids are sick so I was too tired to write.
  • I just wasn’t feeling it today. Maybe tomorrow.

Who are we appeasing? Ourselves, of course. We don’t want to acknowledge our failure or our lack of commitment. It’s easier to excuse ourselves to ourselves than admit we blew it.

What would it look like if we take responsibility instead?

  • I chose to spend my time elsewhere.
  • I elected to focus on something else.
  • I decided not to write while the kids napped.
  • I didn’t care enough to sit down and start.

It might sound a little harsh, but it’s honest, right? And it also requires us to own up to our choices rather than hide behind circumstances or other people.

Life does sometimes get in the way. That’s just a fact. But taking responsibility rather than making excuses gives a much better picture of our writing life and a much better gauge of our resistance.

Do you make excuses for not writing? I still do, even as I want to take responsibility instead. How do you feel after you tell yourself an excuse? A little relieved? A little dirty? I do, and ashamed besides.

How does it feel different to take responsibility? For me it feels a bit grim, but also honest, like a hard look in the mirror. Sometimes it’s clear there wasn’t much I could do. Most of the time, what’s clear is that I was lazy, uncommitted, or scared. Then I get a little mad. Taking responsibility has gotten me back out of bed to do my daily writing because I don’t want to see myself as a person who can’t fulfill her commitments.

For the next week or two, listen to what you tell yourself. Examine the excuses and rephrase them as taking responsibility.  If you need help, call your accountability partner (or get one). Holding myself accountable to another person who wouldn’t accept  excuses was how I began to understand the whole subject in the first place.

If you struggle to get your writing done, ditch the excuses, take responsibility, and get a little mad.

 


Which positive outcomes might we find by moving from excuses to responsibility?