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Crime Scenes for Writers: Fingerprints

Crime Scenes for Writers: Introduction

Crime Scenes for Writers: Fingerprints

Posted on March 1, 2016 by Robyn LaRue | 7 Comments

I’ve been aware that my finger prints are in a federal database for twenty-five years. My husband often jokes that I couldn’t get away with theft or murder because of it. If you were ever employed by an SEC controlled business such as I was, or have worked in a daycare in the last fifteen years, your prints are on file as well.

As far back as 1684, academics lectured on the subject of finger prints. In 1788, Johan Mayer declared our finger prints to be individually unique, but it wasn’t until 1892 that finger prints were used successfully in a criminal prosecution. The man who testified, Juan Vusetech, created a classification of loops, whorls, and arches still used today.

I should interject here that ears, a long-used identifier in Europe, are just as unique as finger prints. However, technology is advanced enough for the matching of foot, toe, and elbow prints as well. Scientists can also match whole or partial palm and heel prints as well, as long as there’s a print with which to compare.

There are two types of finger prints that can be recovered from a crime scene. The first, patent prints, are visible to the naked eye. The second type, called latent prints, must be developed to become visible.

The technique of dusting (using a fine brush of powder above the print, not actually on it) and then lifting a print with tape has been in use since the early 1900s. We’ve come a long way from the black powder and tape method, though. These days there are light powders for dark surfaces, fluorescent powders for textured or multi-colored surfaces (used in conjunction with a black light), and more recently, a laser technique that illuminates the salt and other compounds on the skin’s surface to reveal a clear, photographable print.

For surfaces suspected of holding prints that can’t be raised by more conventional methods, there are two more weapons in the lab’s arsenal. The first involves exposing the surface to vaporized superglue to reveal the print. The second, which is often used only when nothing else works, involves fine gold particles in a metal vacuum to “paint” the prints for visibility. Inroads and successes have also been achieved in lifting prints from skin and porous surfaces.

There are a few limitations to using fingerprints to identify a subject. Since most murders are committed by someone known to the victim, prints are useless unless it can be proven that the suspect has never been at the crime scene or come into contact with the items found there. If the suspect has, for example, often visited his now deceased neighbor, his prints are meaningless to prosecution as they could have been left at any time (unless of course they are left in the victim’s blood). This is a great opportunity for the writer to implicate or draw attention away from a suspect character. If, for example, the reader knows the suspect has been in the house, or has not, but evidence is either to the contrary OR excluded, you ratchet up your reader’s tension.

The other problem with prints is that, while they are unique, they can be quite similar. Print experts use a point system for comparison. Computers are able to match more, but the eight-point match is the baseline. Further points must be matched to eliminate similar prints. It is a time-consuming process and often completed by hand, not computer.

Society is quite aware that finger prints are easily left and easily found, leading more criminals to use gloves. While an actual print can’t be recovered from a gloved hand, size and grip are often evident as the gloves leave something behind as well. And, should the criminal foolishly leave his gloves behind, the prints can be recovered from inside the gloves or on their surface (as part of the process of putting the gloves on).

Prints have been recovered from places people don’t normally think about such as the inside of a belt buckle, a shell casing, the sticky side of duct tape (even after soaking in river water), larger jewelry pieces, paper, faucets, and the undersides of tables, chairs, and countertops. Basically, anywhere someone might rest a finger, a print might be recovered, and the technology will only improve with time.

Because prints are so commonplace and well known to most of us, I think they are often overlooked by both writers and readers, which is a shame. It’s an old method jazzed up by new technology, but still not as sexy as DNA or sensational trace evidence. Still, in the right circumstances, all a jury needs is one single print to convict.

Where is the most unlikely or unusual place you can think of that might yield a finger print?

Crime Scenes for Writers: Fingerprints

Crime Scenes for Writers: Introduction

Crime Scenes for Writers: Reading the Scene

Posted on February 9, 2016 by Robyn LaRue | 3 Comments

Writers and readers should never underestimate a talented investigator’s ability to read a crime scene. On the other hand, they can only “read” what exists. I should note as well that in large departments, detectives or investigators may not arrive at the scene for several hours or even before the body is removed.

Here’s just a short list of things they might look for at the scene of a murder:

Signs of forced entry
Signs of struggle
Activities of the victim before the crime
Activities of the perpetrator both before and after the crime
Location, position, and state of the body
Missing, added, and out-of-place objects
Bullet trajectory
Blood location, trajectory, and characteristics
Observation of environmental conditions
Elements of overkill
Evidence of murder weapon

In addition to the scene itself, investigators gather information such as the last time the victim was seen or spoken to, the last time mail was taken in, anything seen or heard by neighbors or passersby, and the habits of the victim. This information is merged with the information at the crime scene to form a more complete picture. The two sets of information need to be compared and discrepancies reconciled.

The initial theory of what occurred may suggest looking for particular types of evidence or locations to search for fingerprints, DNA, shell casings, stray bullets, and possible trace evidence.

The activities of the perpetrator before and after the crime, such as attempts to clean up the scene, him/herself, posing the body, staging, preparing or eating food or lingering at the scene, and any signs of odd behavior all help police develop information about their suspect, both physically and psychologically. These details are critical to any investigation and provide the framework that police hope will be fleshed out with forensics. This is also a great place to give your reader an obscure clue or a red herring.

The location of the crime and the lifestyle of the victim also give police useable information. A murder that occurs in a suburban home is quite different from one that occurs in a downtown alley in terms of what evidence is visible to the naked eye (and how much evidence must be sifted through and ruled out).

Careful observation and recording of all elements of the crime scene are so important that technology was developed to “map” the scene with a laser in order to recreate it digitally. However, smaller police departments still need to rely on dozens of photos, measurements, sketches, and written notes.

Some investigators will return to the crime scene several times (or more commonly, the photos, reconstruction, or notes). The more experienced and intuitive the investigator is, the more this is helpful. Regardless, it is one of the tenets of investigation that, when you get stuck, you once again begin at the beginning, examining the scene. ViCAP (Violent Criminal Apprehension System), though it has some issues, is also an option for investigators if they suspect the perpetrator has committed similar crimes or they run out of leads.

It is only when there is so little obvious information at the crime scene that cases might hinge purely on what can be uncovered by forensic science. Developing a suspect is more difficult if the victim has been left somewhere other than where he or she was murdered (at a “dump site”), but it’s still possible to gain insight and clues.

Forensics may uncover leads not visible to the naked eye, but the fact remains that the impressions of the investigators at the scene remains the base component of any file. It is also vital information for behavior analysis, or profiling.

Next time, we’ll look at one of the oldest forensic techniques: Fingerprints.

Does your investigative character have special rituals or routines when entering a crime scene?

Crime Scenes for Writers: Fingerprints

Crime Scenes for Writers: Introduction

Posted on February 2, 2016 by Robyn LaRue | 7 Comments

Today’s juries are savvy. Today’s readers are as well. Writers of police procedurals, detective stores, and courtroom dramas need to know their subject. As readers become more sophisticated and enamored of shows like CSI, they expect the authors they select to provide factual information.

Devoted genre readers already know that television has its shortcomings. Though tests and lab procedures are getting faster and more accurate all the time, they are rarely instant, and always subject to the case load ahead in the line. The TV shows only make it look fast and easy.

Not all court cases include plentiful forensic evidence, particularly DNA. Other forms of evidence are just as important in determining guilt or innocence (or even the degree of guilt). This series will cover the most common types: the crime scene, finger prints, blood evidence, ballistics, trace evidence, and DNA recovery.

Just to debunk a few of the most prevalent myths before we get started:

Blood does not stay red or liquid for long.
Bodies begin to decompose immediately. They don’t stay normal-looking and “pretty” for the camera.
Rarely does a pathologist, criminologist (lab technician specializing in forensic testing related to crimes) or medical examiner participate in the detective work.
Crime scene technicians are their own department in most jurisdictions and do not work directly for the detectives or the medical examiner.
The position of coroner is an elected one in many communities. They aren’t always required to be a doctor.
Most autopsies are performed by pathologists. The ME acts as oversight and reviews both lab reports and autopsy results.
The Y incision you see on TV is usually inaccurate. I’ll cover that more clearly in the next series on the body of the crime.
While tests are getting faster and more accurate with advances in technology, most smaller communities don’t have forensics labs and must rely on state labs to handle their cases. It can take months to get test results.

These posts are intended as an overview. I am the first to admit I am no expert, but I’ve done my share of research and was fortunate enough to have conversations with police officers, a forensic dentist, and a former “lab rat” criminologist. I’ll try to provide links for more information if anyone is interested in launching your own research, and please keep in mind that procedures can vary by country. Also, should my information be out of date, I’d love corrective comments, questions, and shared information so we can all learn together and make our stories better.

Investigating crime may rely on the lab, but it always begins when your detective or officer steps onto the crime scene. Next time we’ll look at what can be determined from reading the scene itself.

As a writer and/or reader, how detailed do you like your crime scenes?

Crime Scenes for Writers: Introduction

Crime Scenes for Writers: Fingerprints