Crime Scene Investigator Network Newsletter

AUGUST 2008

Welcome to the August 2008 Crime Scene Investigator Network Newsletter

Multiple Exposure Method in Digital
Photography of Fingerprints

Alan Chaikovsky, Uri Argaman, Alex Balman,
Laser Sin-David, Avner Barzovski, and Uri Yaalon

From the Journal of Forensic Identification
Vol. 55, No. 5, September/October 2005*

Abstract: Forensic latent fingerprint photography, performed with evidence that has a substrate that is not uniform in terms of shape, color, and so forth, requires the use of various techniques. This report will introduce the multiple exposure method using digital photography and computerized image processing using layers methodology.

Background
Latent fingerprint (latent) photography normally requires the use of various lighting techniques to overcome the problems encountered with some surfaces upon which latents are discovered. Sometimes it is difficult (or impossible) to capture, in a single exposure, all of the detail using a single lighting technique. This problem is frequently encountered on curved surfaces because multiple light angles cannot provide the optimum simultaneous illumination to all portions of the print. Problems may also be encountered when multiple excitation wavelengths or different filters are needed to provide proper exposure for different areas in the same latent.

In conventional forensic photography, there are various solutions to the problems mentioned above. For example, when a light source does not cover the total area of the latent, the painting with light technique can be used. Another technique that is used in such cases is superimposition (i.e., double exposure of two images, one on top of the other, exposed on the same film frame). This technique is complex and is not frequently used in forensic photography. On the other hand, the digital multiple exposure technique is simple and productive because the merging of multiple images is more easily controlled in the computer. To the best of our knowledge, this digital method is a new application of an old technique and has not been previously reported.

Introduction of the Method
The main advantage of multiple images combined into one image is that this allows improved visualization of selected portions of a latent without affecting the rest of the image. The layers are similar to transparency pages that can be superimposed or placed one on top of the other. When there is an image on an upper layer, it is possible to see the lower layer through the use of a layer mask.

The multiple exposure technique is the superimposition of two or more separate photographs of the same latent, taken with a digital camera, while the physical position of the camera and the subject (the latent) are absolutely steady.

Because several parameters may vary, the entire process must be fully documented. The parameters that may be changed between the different photographs include the light source angle, the light source, the wavelength of illumination, and the exposure. Ideal parameters vary according to the topography of the surface area, the nature of the surface, or the location of the latent within that area.

Because the photographs are taken with a digital camera, it is very important to keep the file format (the RAW format should be used when available) and size constant. The reason for this is that a change in file size may prevent the precise alignment between the photographs when they are superimposed on separate layers.

After the photographs are taken and a separate original file is retained for each photograph, a composite Photoshop Document (PSD) is created with the Adobe Photoshop software; this file format will allow a separate layer for each image. (Other image processing programs may have similar functions and capabilities.) When creating the composite file, it is important to understand that the alignment of the different layers is critical.

< read the complete article and view example photographs >

*From the Journal of Forensic Identification Vol. 55, No. 5, Sept/Oct 2005.
The Official Publication of the International Association for Identification "Reproduction of the Journal of Forensic Identification, in whole or in part, for noncommercial, educational use is permitted provided proper citation of the source is noted."

In This Issue
New CSI and Forensic Job Announcements

Featured Forensic Program

CSI In The News

Resources on the Crime Scene Investigator Network Website

Learn How to Become a Crime Scene Investigator

T-Shirts from ForensicWear.com

New CSI and Forensic Job Announcements

Forensic Section Supervisor | City of Santa Monica, California
Final Filing Date: August 28, 2008
$6,066.00 - $7,489.00 per month
Oversees latent fingerprint recovery methods, crime scene preservation, physical evidence collection, DNA recovery, photographic, video and computer imaging tasks relating to criminal investigation and the prosecution of criminal cases. Administers and coordinates the Forensic Section and supervises assigned staff.
<View complete job listing>

Crime Scene Technician | Tacoma, Washington Police Department
Final Filing Date: September 1, 2008
Salary: $22.78 to $27.96 per hour
Crime Scene Technicians perform specialized, technical work gathering, processing and preserving evidence at crime scenes in support of law enforcement activities. Examples of work include but are not limited to detecting, collecting, preserving, packaging, and transporting evidence; processing for latent fingerprints; performing forensic photography and producing crime scene diagrams. Crime Scene Technicians also prepare comprehensive written reports and testify in courts of law.
<View complete job listing>

Criminalist I / II | San Mateo County, CA Sheriff’s Forensic Laboratory
Final Filing Date: September 04, 2008
Salary: $5,470.40 - $8,515.87 per month
The successful candidate for this position must have knowledge of general criminalistics and a good understanding of one or more of the following: Forensic Biology, Controlled Substances, Trace, and Blood/Breath Alcohol Testing.
<View complete job listing>

Principal Forensic Print Specialist | City of Los Angeles, California
Final Filing Date: September 4, 2008
Salary: $90,932 to $112,981 per year
A Principal Forensic Print Specialist plans, organizes, and directs the work of Senior Forensic Print Specialists, Forensic Print Specialists, and other personnel engaged in searching for, developing, and lifting latent prints at crime scenes; comparing prints with other prints for identification purposes; acts as the department expert authority on latent print matters; applies sound supervisory principles and techniques in building and maintaining an effective work force; fulfills equal employment opportunity responsibilities; and does related work.
<View complete job listing>

Identification Lab Manager | City of Lincoln, Nebraska
Final Filing Date: September 5, 2008
Salary: $47,347 - $81,040 per year
Lincoln Police Department/Administrative Support seeks individual for supervisory and administrative work; directing and coordinating the operations of the Identification Unit; examining and comparing questioned documents; analyzing, classifying and filing, and identifying fingerprints; operating the NAFIS computer system; writing reports or identifications; preparing and giving expert witness testimony; and maintaining the Digital Imaging System and evidence files and records.
<View complete job listing>

Forensic Analyst | Eugene, Oregon, Police Department
Final Filing Date: October 10, 2008
Salary: $25.41-$32.40 per hour
Performs a variety of complex and specialized technical tasks collecting, preserving, and identifying criminal evidence at the crime scene and/or analyzing evidence in the laboratory; analyzes evidence in conjunction with investigation activities and provides expert testimony in court on methods and results of analysis.
<View complete job listing>

Search for more job listings in Crime Scene Investigations and Forensics
<Crime Scene Investigator Network Employment Listings>

Featured Forensic Training Program

Eagle Crime Scenes, Inc., brings you a multimedia, software version of their highly-successful crime scene processing manual that combines text with full-color photographs and videos that will take you through the steps of processing crime scenes right in the field! Simply insert the data DVD in your laptop computer and select the lesson you need to review. Can't remember how to apply amido black to a tile floor? Just select the video and you'll be shown all the steps you need to know to properly get the job done. Learn more at: Eagle Crime Scenes, Inc.

CSI In The News

<Local Forensic Unit Uses High Tech Equipment>
A crime-fighting machine that's been shown on investigative programs can now been found right in our own backyard. Now, the Thomas County forensics team is using the high-tech device to help solve crimes. "It's just now starting to tap into the law enforcement community. I think there's just a handful in the country I believe," said Andy Forte, Thomas County Forensic Investigator. The $180,000 Leica 3-D Laser Scanner was given as a grant from Homeland Security to the Thomas County Sheriff's office.
WCTV – Tallahassee, FL, by Caroline Blair – August 21, 2008

<More women choosing careers in forensic science>
NKelly Johnson snips pieces from a blood-stained, blue-striped shirt, then swabs the neck and armpits for sweat. Down the hall, Samantha Glass watches as a chemical reaction reveals a fingerprint on a juice bottle. In the state's Eastern lab, Julie Price fires a .45-caliber pistol into a long metal water tank. Unlike their counterparts on TV, they're not wearing low-cut shirts or stiletto heels, and their hair and makeup aren't always perfect. These are the real women of forensic science, and there are plenty of them. An Associated Press review of accredited forensic science programs in the United States found about 75 percent of graduates are women, an increase from about 64 percent in 2000. Women say they were drawn to forensic science by strong role models, a desire to help people and stability that's often lacking in other scientific careers. Those in the field estimate that the nation's forensic labs are at least 60 percent female. At Virginia's Department of Forensic Science, 36 of 47 scientists hired since 2005 were women.
The Associated Press, by Dena Potter – August 15, 2008

<Forensic unit is recognized for meeting international standard>
The eyes of the crime scene analyst at the Ventura County Sheriff's Department's Forensic Sciences Laboratory seemed to be absorbed by the slide underneath the powerful microscope lens, gently guided by slow-moving fingers. In the brightly lighted room, there is an intensity as forensic scientists help police hunt down the human source of DNA left at a crime scene or, perhaps, a footprint or tire print found next to a human body. Paying careful attention to detail and keeping track of thousands of slide samples and other items is part of a job where an error could mean a guilty suspect is set free or an innocent person might face years, even decades, behind bars.
Ventura County Star – Camarillo, CA, by Raul Hernandez – August 4, 2008

Other Resources on the Crime Scene Investigator Network Website

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