T  H  E      D  E  T  A  I  L

Monday, October 6, 2003

Good morning via the "Detail," a weekly e-mail newsletter that greets latent print examiners around the globe every Monday morning. The purpose of the Detail is to help keep you informed of the current state of affairs in the latent print community, to provide an avenue to circulate original fingerprint-related articles, and to announce important events as they happen in our field.

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Last week, we re-published "The Myth of Fingerprints", by Michael Cherry.  This week, we realize that Michael Cherry is a regular reader of the Weekly Detail, and he provides us with his supplemental comments on his article published last week.

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Good morning, and thank you for taking a moment to read my comments regarding my article "The Myth of Fingerprints." I asked Kasey to publish this because I feel strongly about this subject, and I sincerely desire for everyone to know the reasons behind the article.

Even though I have some training and knowledge of fingerprints, you will not see me testify as a fingerprint expert. I am not a fingerprint expert, and I would never claim to be a fingerprint expert. Likewise, I would not expect to see someone testify to the results of a fingerprint enhancement unless at a minimum, they understood the analog to digital and digital to analog conversions that took place as well as the strengths and weaknesses of the equipment used.

Some examiners may have no choice, if they want to keep their jobs. They may be required to present an altered image in court. The bottom line is this: If I produced a second enhanced version of the same latent fingerprint in a case and you were asked which enhanced fingerprint is the correct one; Unless you are both a fingerprint expert and an imaging expert your answer would be "I do not know."

My intent is not to disrespect the value and contribution of fingerprint examiners. My intent is to improve the quality of the equipment and procedures used to perform fingerprint enhancement. But why would anyone budget money for training or improved equipment if a fingerprint enhancement case has never been seriously challenged in court?

As many of you know, I was involved in Reyes v Florida. Every day, fingerprints are routinely enhanced, yet there have been no fingerprint enhancement challenges since Reyes. And to provide a level of comfort for now... even though the tone of my NACDL article is a call-to-arms, I have not yet received even one inquiry from a defense attorney or public defender’s office. And I have heard estimates that criminal defense attorneys loose between 90 and 95% of their cases.

I have also asked Kasey to distribute my other article, "Reasons to Challenge Digital Evidence and Electronic Photography."

If you have any questions or interest, please don't hesitate to contact me as some already have. If we get enough responses, perhaps we can conduct a training session.

Reasons to Challenge Digital Evidence and Electronic Photography
by Michael Cherry
Originally written for the NACDL Champion; reprinted here with permission of the author.
02 June 2003

If digital evidence can be incorrectly altered or enhanced¹ by newly trained personnel, and digital cameras² and printers³ are not equal to their film counterparts in quality and color, what does that say about the quality of today’s forensic evidence which is transitioning to digital?

Examples of digital concerns:

• Digital cameras do not accurately represent color.

• Dye-sublimate digital printers can even confuse imaging experts. They cannot produce the highly accurate photographic images that film does, but their images appear to be photographs. They produce color and negative prints on photographic style paper that mimics the look and feel of photographs.

• In many instances, the digital printer used is not as accurate as the digital camera used, and therefore crime scene details and fingerprint minutiae is lost.

• The law enforcement community is incorrect regarding the acceptability of using traditional darkroom enhancement techniques on digital images “…Traditional enhancement techniques are techniques that have direct counterparts in traditional darkrooms. They include brightness and contrast adjustment, color balancing, cropping, and dodging and burning.

These traditional and acceptable forensic techniques are used to achieve an accurate recording of an event or object⁴.” Many different forms of image enhancement and traditional darkroom image enhancement can render some crime scene details and fingerprint minutiae unprintable. For example, Dodge-and-burn, the selective lighting and darkening of areas within an image, can place details outside of the threshold of a digital printer’s range of light and dark printing capabilities.

• The law enforcement community is incorrect with regard to the discovery of image enhancement. “Question: is it necessary to document the enhancement process used to produce an enhanced image? Answer: the need to document the enhancement process is determined by the process used. Discussion: documentation of enhancement steps is not necessary when using traditional darkroom techniques⁴.”

• The transition to digital images requires a brand new level of standards, guidelines and training. For example, the use of image editing and enhancement software should be curtailed or at least regulated. Before and after images should be routinely provided. This is essential when the original evidence is not is not available or well preserved. Examples include hard to- lift fingerprints, footprints, bite marks and tire patterns.

• There are known quality problems associated with some digital printers, scanners and cameras. For example, some digital printers are famous for their fading pictures, others for their magenta cast.

• Digital images should be challenged when the original image is not available for comparison. Examples; include hard-to-lift fingerprints, footprints, bite marks and tire patterns. There are many reasons to challenge including authenticity, accuracy and the quality of hacker-free security procedures.

• Digital images should not be compressed to save space unless a loss-free method is used.

• All enhancements should be challenged, as they require very precise steps and newly trained personnel may find them difficult to understand or implement. This is particularly true of audio, video and fingerprint enhancements. Enhancements of enhancements should be regulated. There is a relevant challenge for any form of digital image or digital enhancement associated with audio, video and fingerprint images.

The Iowa International Association for Identification (IAI) Web site highlights State v. Hayden, 950 P.2d 1024 (Wash. App. 1998),where the Washington court of appeals noted experts’ claims “that digital photographs are superior to regular film photographs because digital photographs can pick up and differentiate between many more colors and shades of gray than film photographs. Digital cameras do not accurately represent color.

I did not realize how rapidly the criminal forensics community was transitioning to the use of digital technology until I watched CBS News 60 Minutes II the Hidden Clue, “Detectives now have a new tool for cracking even the toughest of cases,” Jim Stewart reports. “Known as digital fingerprint enhancement, it’s become the silver bullet among police forensic units all across the country……..”⁵

As a voting member of the evidentiary committee of The Association for Information and Image Management (AIIM)⁶ and a pioneer in image management and digital photography going back to early NASA days, I know it’s very difficult to perform a proper enhancement, particularly a fingerprint enhancement.

Digital enhancement is highly controversial within the imaging community. The product of a digital enhancement is a new image which is identical to old one, except for its altered characteristics. For example, the red car image now has a twin, a blue car image.

In the courtroom enhanced digital images are original images that have undergone some computer changes, and it falls to the discretion of a trial judge as to whether they are admissible as duplicates. I would like to classify enhanced digital images as enhanced digital images and not as originals or duplicates. I would also like to number enhanced images to readily identify their lineage.

An image derived from the source image would we a first order enhancement, an image derived from that image would be a second order enhancement and so on. As two or more enhanced images can be spawned from the source image, I would like to see them alphabetized e.g. image 2a and image 2b.

Mathematical enhancements include: magnification, color substitution and the removal of a thin nylon stocking or mask covering the features of a persons face. After removal, the nose shape, chin type and the presence or absence of a mustache or beard can often be determined.

Mathematical enhancements can be quite powerful. Unfortunately, it is not uncommon for mathematical enhancements to be performed incorrectly as we are in a transitional period from analog to digital.

Artistic enhancements can be used to do anything: selectively darken or lighten areas within an image (Dodge and Burn), place a person within a picture or video as well as to modify conversations within an audio or video recording. Artistic enhancement can lead to pure fantasy.

All enhancements should be challenged as they require very precise steps and newly trained personnel may find them difficult to understand or implement. This is particularly true of the audio, video and fingerprint enhancements. In addition it is not uncommon to see artistic and mathematical enhancements on the same newly created image.

On the positive side, scientists are having some success in enhancing low quality videotape commonly found in gas stations and convenience stores. While not necessarily ready for the courtroom, the results of these improvements can be very useful in determining the probable absence or presence of a specific person.

Some concluding thoughts:

• Are there known quality problems associated with the digital printer, scanner or camera used?

• If enhanced images are introduced, were the enhancements correctly done? Can they be repeated using a different person?

• Enhancements of enhancements shouldn’t be allowed as they are unnecessarily misleading.

• Digitally enhanced pictures should be identified as such.

• If digital images are compressed was a loss-free method used? If not, why not?

• Digital images should be challenged when the original image is not available for comparison.

• During today’s cost-driven transition period to digital, both the quality of the images and the experts tend to be inferior to their analog counterparts.

• Text files that describe the evidence should be properly safeguarded.

Notes

1 The product of a digital enhancement is a new image which is identical to old one, except for its altered characteristics. For example, the red car image now has a twin, a blue car image.

2 Kodak T-MAX 100 can resolve approximately 200 line pair per mm TOC 1000:1, Kodak Web Site, 200 pixels/mm at 35mm resolution 36*200*24*200=34,560,000 or 34 Megapixels In conventional digital cameras systems, color filters are applied to a single layer of photodetectors in a tilted mosaic pattern. The filters let only one wavelength of light - red, green or blue - pass through to any given pixel, allowing it record only one color. As a result, typical mosaic sensors capture 50% of the green and only 25% of each of the blue and red light. The approach has inherent drawbacks, no matter how many pixels a mosaic-based image sensor might contain. Since they only capture one third of the color, mosaic-based image sensors must rely on complex processing to interpolate the two-thirds they miss. Not only does this slow down the speed of image rendering, interpolation also leads to color artifacts and a loss of image detail. Some cameras even intentionally blur pictures to reduce color artifacts. http://www.pctechguide.com/

3 Computer printers print at 300 to 2400 dots per inch. Film requires at least 8000 dots per inch. Sales terminology can be misleading, 4800 and 5760 optimized dots per inch (dpi) are used to describe printers that i mprove the appearance of basic 1200 x 1200 dpi images. These printers can not accurately print 4800 or 5760 dpi input images. Some drum scanners can scan 35mm film at 11,000 dpi. (Bob Myers, Heidelberg USA, Inc.)

4 The National Association of Criminal Defense Lawyers, Inc. (NACDL) Standards and Guidelines, Recommendations and Guidelines for the Use of Digital Image Processing in the Criminal Justice System Scientific Working Group on Imaging Technologies (SWGIT) Version 1.2, June 2002.

5 The product of a digital enhancement is an identical twin image, except for its altered characteristics. Examples include a red gun instead of a blue gun or the removal of an extraneous pattern, the weave of a bed sheet, to make the new fingerprint image more apparent.

6 AIIM holds the secretariat for International Standards Organization (ISO) ISO/TC 171 SC2, Document Imaging Applications, Application Issues. AIIM is also the administrator for the U. S. Technical Advisory Group (TAG) to ISO TC 171, Document Imaging Applications that represents the United States at international meetings. Over 80 of AIIM's standards, recommended practices and technical reports have been drafted and approved by the American National Standards Association (ANSI).

About the Author
Michael Cherry, is a principal in GMC7 Inc. He assisted NASA in the development of imaging displays used by the Apollo Moon Flight Simulator for Celestial Navigation. He worked with Lou Cataldo, to automate his early single fingerprint system. He collaborated with Sony Labs in the development of color imaging products and he joined with IBM Imaging Labs in numerous efforts including the capture and display of digital camera images. He has published articles for the US National Institute of Standards and Technology (NIST). He is a Giga expert and a voting member of the evidentiary committee of The Association for Information and Image Management (AIIM).

Michael Cherry
GMC7 Inc.
51 Saddle River Road
Woodcliff Lake, NJ 07677
201 513-8300
Fax 270-738-0134
E-MAIL: mc@gmc7.com

Copyright © 2003, The National Association of Criminal Defense Lawyers, Inc. (NACDL) All Rights Reserved.
 

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FUNNY FINGERPRINT FINDS

The folder is empty.  :(  Keep your eyes peeled for FFF's!!

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