Legal Ramifications of Digital Imaging in Law Enforcement

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October 2000 - Volume 2 - Number 4

Legal Ramifications of Digital Imaging in Law Enforcement

Erik C. BergForensic Services Supervisor

City of Tacoma Police Department

Tacoma, Washington

Introduction|Digital Image Basics|Digital Imaging and Chain of Custody

What Is an Original?|Documenting a Digital Image|Image Tampering|Conclusion

References

IntroductionSome of the information in this article was presented in 1997 at the International Association for Identifications(IAI) 82nd Annual Training Conference in Boston, Massachusetts. At the time,

only a handful of law enforcement agencies were using digital imaging for casework. Of those, the majority were using it only for specialized work, such as the enhancement of latent

ingerprints. Interest in digital imaging was growing rapidly. The IAI passed Resolution 97-9, which recognized digital imaging as a scientifically valid and proven technology for the first time.This offered legitimacy to the technology and encouraged its adoption among the members of the IAI. Since that time, digital-imaging technology has spread to nearly every major law

enforcement agency in the United States. The capability of the technology has continued to expand at an amazing rate. The use of digital cameras is no longer restricted to capturing latent

ingerprints or other specialized purposes. More and more agencies are choosing digital capture systems to eliminate the need for film-based imaging systems. The potential for budgetary

savings and the ability to deliver images faster continue to drive more law enforcement agencies toward a conversion to digital imaging. Rapid moves toward any technology, without adequate

esearch and planning, or the training needed to demonstrate competency and proficiency, can leave an agency vulnerable to misinformation and legal challenges.

An article entitledDigital Imagery in the Courtroom , published by Kodak (1999) on the Internet, states that Imageryis not evidence.Most experienced forensic photographers would challenge

he accuracy of this statement, because the author fails to recognize that there is a difference between an image or a chart introduced for illustrative purposes and an image submitted as evidence.
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According to BlondsEvidence(Blond et al. 1994), photographic evidence can be authenticated by two methods, depending on the type of imagery. The traditional method is to consider images

as illustrativeof a witnesstestimony.Given the advances in imaging technology, many jurisdictions have adopted an alternative method on the basis of thesilent witness theory, which states

hat photographic evidence speaksfor itselfand is thus admissible through testimony that establishes how it was produced. It is ironic that one of the first sentences in the articleDigital

Imagery in the Courtroomstates that there is muchconfusionabout the subject of admissibility of digital images in court. Most of the confusion about digital imaging stems from a lack of

nowledge about both the technology and what it can do and how the legal system scrutinizes new methods.

Any agency contemplating digital imaging technology would be wise to seek out as much information on the subject as possible. Particularly relevant is how the local magistrate is going to react

he first time a digital image is introduced in court. Every state and federal court in the United States has a published set of court rules that, among other things, outlines the process of how

arious types of evidence and testimony can be received by the jurisdiction considering the case. BlacksLaw Dictionary(Nolan and Nolan-Haley 1990) devotes two pages to the subject ofevidence and includes a brief discussion of how evidence is authenticated. Prosecuting attorneys as well as defense attorneys are excellent sources of information about how a new technology

ight be received if it were introduced in a case they were involved in. Some attorneys will even tell you how they might attack the evidence.

In general, attorneys treat anything new and lacking in previous case law with suspicion. Scientific evidence is admissible only if the principle upon which it is based is sufficiently establ ished

to have gained general acceptance in the field to which it belongs(United States v. Kilgus 1978). From 1923 until 1993, the process for determining whether a scientific process had gained

general acceptance was determined in aFryehearing (Frye v. United States1923). In 1993, the federal courts adopted a more restrictive standard known as Daubert(Daubert v. Merrell Dow

Pharmaceuticals, Inc.1993). Since that time, a number of state courts have also adopted Daubertas the standard they use for determining the admissibility of scientific testimony. How this will

affect digital imaging remains to be seen, but it is likely that we will see more scrutiny by the court rather than less.

Cost is always a consideration when making a decision to replace one tool with another, but the real questions that need to be answered are: What is the most effective tool for the job at hand?

What are the consequences of that decision? An unidentifiable latent fingerprint lifted from a crime scene is of virtually no value. A photograph of that same latent fingerprint is equally useless;

it just costs more to recover. A digital image of that fingerprint costs very little to capture, but if it is subsequently enhanced and then identified as a result of the enhancement process, any

aterial costs associated with the capture of that fingerprint become irrelevant.

A lack of understanding or misinformation about the use of digital imaging can contribute to poor budget decisions and wholly inadequate statements about policy and procedure. This can leavean agency or potential witness in a precarious position when it comes time to testify in court. The basis of any expert testimony is predicated upon superior knowledge of or possession of

specialized experience with a particular subject.

Back to the top

Digital Image BasicsThe process of creating a digital image is a

simple principle to understand. Light falling

pon a grid of detectors known as a charge

coupled device, or CCD, produces a pattern of

electrical charges that are measured,

converted to numbers, and then stored. The

rocess can be analogous to a group of water

glasses set out in a grid pattern to collect

ainwater. The amount of water collected in

each glass will vary according to the patternof the rainfall at any given point above the

glasses. Once the rain has stopped, the glasses

are collected and carried one at a time, much

like a bucket brigade, to a metering device.

The metering device measures the quantity of

ater collected in each glass, converts the

amount to a number, such as six ounces, and

hen records the amount before moving on toAs the analog, or continuously

ariable, rain falls across the
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he next glass. glasses in a random pattern, theater is collected and measured.

Light falling upon a CCD

roduces a pattern of electrical

charges, which are converted to

umbers and then stored.

In a digital image, the quantity of light collected by each sensor, or glass, is measured by the metering system and recorded as a number. This number is stored in the same grid position as the

sensor that collected the sample. As each subsequent sample is measured, its value is stored according to its position in the original grid of sensors, or glasses. Each value in the grid corresponds

o a picture element (also known as a pixel) in the digital image. Each pixel is displayed on a computer monitor, beginning in the upper left corner, by a tiny light bulb that takes on a particular

color or shade of gray according to the number recorded for the grid point it represents. The computer reads the number assigned, checks an index of colors to determine its color equivalent, and

hen adjusts the corresponding light bulb (pixel) on the computer screen to match the color value. The computer then moves on to the next pixel in the grid, repeating the process until all the

ixels in the image are displayed on the computer screen. The end result is a mosaic of dots that fit together and represent the original scene.

The illustration at right shows a portion of a

digital image in numerical form with the gray

alue of six different pixels represented by an

enlarged circle. The accuracy and detail of a

digital image are dependent upon both the

esolution of the optical system used in the

capture device and the density of the sensors

on the CCD. Generally, more sensors means

a more accurate and detailed image

epresentation.

Pixel code values from a

typical digital image. Code

alues shown are in

exadecimal. The equivalent

gray tone is shown for

selected pixel values.Photographic film records an image using light-sensitive collectors called silver halide. As light strikes the surface of the film, individual particles of silver halide change chemically. The longer

he exposure, the greater the change. When the film is processed, exposed silver halide is reduced to fine silver particles in proportion to its exposure to light. The final negative represents the

original image as a mosaic of fine, irregular particles of silver. The accuracy and detail of the image are dependent upon the resolution of the optical system used in the camera, as well as the

density and size of the individual silver halides in the film. By populating a piece of film with finer particles of silver halide, it becomes possible to record more individual samples of light withinhe same area of film. In general, just as a CCD with more sensors can record a more accurate and detailed image, so too can a piece of film that is populated with fine rather than course silver

alide particles. The actual process of capturing an image on photographic film is a bit more complex than the simplified explanation provided here, but for the purposes of this article, it should

e adequate to show the similarities between a typical CCD and photographic film. The similarities should be enough to dissuade anyone who has used a camera from believing a digital image is

he result of some novel scientific process. Few would dispute the ability of photographic film to record an image accurately. The world has taken photographs for granted since the first

daguerreotype was presented on August 19, 1839 (Crawford 1979). Digital images, on the other hand, still represent a mystique when shown to the average citizen, and the origin and validity of

digital images are looked upon with some suspicion. This is especially true when the image is introduced into a legal proceeding. Defense attorneys and judges tend to be distrustful of

echnology. Jurors are easily confused by technical explanations, placing more credibility upon what they can see and touch.


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The general population watches satellite views of the changing weather patterns above their neighborhoods, displayed every night on the evening news, without realizing they are looking at

digital images captured by digital cameras mounted on a platform floating in space. Few would question the accuracy of the images depicted, and most take them for granted as they plan their

day around the information the images provide.

Back to the top

Digital Imaging and Chain of CustodyEarly adopters of imaging technology include forensic professionals Alan McRoberts of the Los Angeles County SheriffsDepartment, Ed German of the U. S. Army, William Watling of the

Internal Revenue Service, and Brian Dalrymple of the Ontario Provincial Police Department. Since early 1987, when Alan McRoberts presented imaging as a way to enhance latent fingerprints

at an FBI symposium, digital imaging has gained widespread acceptance among the many professionals working within the forensic sciences. As the use of digital imaging becomes morecommon among the various law enforcement agencies, throughout the United States and Canada, acceptance by the legal community will be the result of proper procedure and conformity to

established rules of evidence. One of the more important rules that need to be considered when using digital imaging technology to collect physical evidence is chain of custody.

An early and defining case,Albert Lopez Gallego v. United States of America, decided in the Ninth Circuit Court of Appeals on March 23, 1960, helped set the standard for admission of physical

evidence. The defendant, Albert Lopez Gallego, was convicted of unlawful importation of marijuana. At issue was a can and bag containing marijuana. The defense asserted the marijuana

evidence was unaccounted for between the confiscation of evidence from the defendant and its subsequent introduction at trial. The Court of Appeals applied the following litmus test:

Before a physical object connected with the commission of a crime may be properly admitted in evidence, there must be a showing that such ob ject is substantially in the same condition as when

the crime was committed. Factors to be considered in making the determination of whether a physical object connected with the commission of a crime is in substantially the same condition as

when the crime was committed, so that it may be admitted in evidence, are nature of article, circumstances surrounding its preservation and custody, and likelihood of intermeddlers tampering

with it; if upon consideration of such factors the trial judge is satisfied that, in reasonable probability, the article has not been changed in important respects, he may permit its introduction as

evidence.

Why this particular test is relevant to digital imaging will be shown in the following discussion.

On August 21,1986, the Texas Court of Appeals affirmed the conviction of defendant Gary Wayne McEntyre ( Gary Wayne McEntyre, Appellant, v. The State of Texas, Appellee) for solicitation

of capital murder. Several issues were addressed in this case, but the issue most relevant to digital imaging was the admissibility of audio recordings of McEntyresconversations with an

ndercover informant. McEntyre claimed that a seven-minute gap in the audio recording was proof that the tape had been altered. The State of Texas claimed that the gap in the recording was a

esult of interference and that the recording had not been changed or altered in any way.

The appellate court applied several tests to determine the admissibility of the tape recording:

The particular case in which a recording is offered is part of the circumstances to be considered in determining whether chain of custody has indisputable fundamental trustworthiness necessary

or the recordingsadmission into evidence. The burden is on the proponent to establish the necessary predicate for admission of the tape recordings. If alteration of a tape recording offered in

evidence is accidental and is sufficiently explained so that its presence does not affect the reliability and trustworthiness, recordings can be admitted. When the defendant makes an attack on the

chain of custody of a tape recording offered in evidence, the burden of disproving authenticity is not shifted to the defendant.

The court in this case used a much narrower criteria for determining proper chain of custody. Gallego stated that evidence must be in substantially the same condition. McEntyre defined chain of

custody, when applied to tape recordings, as demonstratingto the court that nothing occurred that would affect the trustworthiness or reliability of the tapes.

The finding in this case was that the tape recordings of conversations between the party equipped with a police transmitter and the defendant regarding solicitation of murder were notsufficiently altered to make the recordings inadmissible. This was supported by testimony of the recorder operator that unclear portions in the recording were due to interference and that the

ecording had not been changed or altered in any way, notwithstanding the seven-minute gap in the tape was due to a loss of transmission from the microphone. Police testimony established that

he tapes were kept in a locked steel cabinet in the police departmentsevidence room and that when the tapes were signed out by district attorney staff, no one else had access to them. The court

ound that the state established proper chain of custody of the recordings of conversations between the informant and McEntyre and that the recordings were admissible in the defendantstrial

or solicitation of murder.

Chain of custody can be one of the most difficult issues faced by the forensic professional trying to introduce a digital image as evidence in a criminal case. If a defendant alleges an image has

een altered, or could have been altered, the burden of proof falls upon the state to prove otherwise. If the image is a fingerprint linking the defendant to a crime scene, it is inevitable that the


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The last sentence in 1550.6 defines the burden of proof when an issue is raised regarding the authenticity of an image. It appears to be a subtle refinement of Gary Wayne McEntyre v. the State

of Texas, discussed earlier:

If any party to a judicial p roceeding introduces evidence that such a printed representation i s inaccurate or unreliable, the party introducing it into evidence shall have the burden of proving , by

a preponderance of evidence, that the printed representation is the best available evidence of the existence and content of the images that it purports to represent.

Back to the top

Documenting a Digital ImageA defensible procedure that reasonably protects an original image will minimize the risk of losing an image during a suppression hearing. An open and consistent procedure designed to

inimize access to the original image will help to eliminate any question of impropriety that might be raised and presents an appearance of fairness and professionalism.

Any process used to enhance a digital image must be reproducible by a third party who has similar training and experience. Enhancement processes should be documented sufficiently to allow

or the recreation of enhancement results. Any software used to enhance an image that is subsequently used as proof in a criminal matter could become the subject of either

aFryeorDauberthearinga type of suppression hearing designed to determine the validity of any new scientific methods (Frye v. United States 1923;Daubert v. Merrell Dow

Pharmaceuticals, Inc.1993). Prior to aFryeorDauberthearing, a defense attorney could demand access to the source code for any software that was used during the image capture and

enhancement process.

Source code is the basis of all computer

rograms and consists of a structured set of

instructions that tells a computer how to

erform specific operations, such as saving

an image or increasing image contrast. The

source code is written in an English-like

rogramming language and is proprietaryo the company that produces it. The last

step in the process of creating a computer

rogram is the conversion of the source

code from English to binary machine code,

hich is made up of ones and zeroes. Once

converted, a computer can execute the

rogramsinstructions, but anyone

attempting to inspect the binary code will

see only undecipherable gibberish. It is

ormally impossible to reconstruct a

rogramssource code from the binary

achine code, so proprietary programming

echniques and methods are safe from

disclosure to competing companies.Defense attorneys trying to gain access to a

computer programssource code might

argue:

Modern computer software is

extremely complex. The few linesof code shown here represent a

ery small portion of the source

code required for the most

common filters used to enhance

digital images. Most image

enhancement programs contain

alf a million or

ore lines of code.
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Click on the image for an

enlarged view of the source code.Given the myriad of algorithms used to filter and process digital images, it is conceivable that an error in one or more of the algorithms used to process this image could have created a defect. It

is also conceivable that the resulting defect in the image leads to an erroneous conclusion by the witness in this case. Before we can properly cross examine this witness about the enhancement

rocess used, and in order to establish whether or not such an error could have occurred, it will be necessary for our expert to examine the source code for all the software used to alterthis

image.

A number of other, similar arguments could also be raised to cast doubt upon the image and the process used to create it.To gain access to a manufacturerssource code, the defense would normally have to agree to the terms of a nondisclosure agreement to prevent the disclosure of any proprietary information. In

ost cases, the manufacturersattorneys are going to be presenting their own arguments against disclosure. If the manufacturer of the software is successful in denying access, the defense could

ove to suppress any results that were derived through the use of that software. The source code of any software program is generally considered a trade secret by its owner and is protected with

great vigor. Agencies considering the use of any software for the purposes of image enhancement should obtain assurances from the manufacturer that if it should become necessary, they will

allow a defense attorneysexpert to inspect their code.

Modern computer software is extremely complex. Any alleged defects would take an expert unfamiliar with the source code months or even years to find. Once found, it would likely take

onths more to show the errors created a defect sufficient to lead to an erroneous conclusion. A defense attorney who files a motion designed to gain access to the source code of a software

roduct, such as Photoshop, is gambling that the manufacturer is going to successfully deny access. Preplanning can help deflect this kind of argument and save considerable grief.

A defensible procedure for documenting a digital image can mean many things to many people. Any procedure designed to protect the chain of custody must, at a minimum, be able to address

he following questions:

Who captured the image and when?

Who had access to the image between the time it was captured and the time it was introduced in court?

Has the original image been altered in any way since it was captured?

Who enhanced the image and when?

What was done to enhance the image and is it repeatable?


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Has the enhanced image been altered in any way since it was first

enhanced?

How these questions are addressed depends on many factors, including department policies and the policies of the local prosecutor. The important thing to remember is that a digital image used

in a legal context is evidence and must be treated as such. The goal of any effective image-tracking procedure should be to eliminate the opportunity for unauthorized persons to access images,

hus avoiding the argument that someone could have altered or substituted an image. Procedures range from simple to sophisticated.

Various methods have been devised to authenticate the integrity of digital images once they have been captured. Many rely on some type of software system to validate the images. Some

systems document the chain of custody by tracking image capture and enhancement processes and restricting access to authorized personnel. One system, in particular, stores a mathematically

nique value for each image as part of the tracking process. Any changes made to the image can be detected immediately. The process is designed to answer questions about the integrity of an

image without altering the actual image information in any way. Any changes that occur during the enhancement process are restricted to a copy of the original image. All changes can be

ecorded as part of the tracking process.

Other methods use an encryption scheme to scramble the image information, making it impossible to view the image without knowing the encryption key. This might be sufficient to prevent any

eaningful tampering, but the encryption process itself alters the original image data. In order to view an encrypted image, it must first be reconstructed. Once encrypted, the original

nencrypted image is not retained. The encryption process alone does nothing to document the chain of custody. In addition, encrypting large images can take a significant amount of time;

especially when there are more than a few images being encrypted.

A third approach is based upon an ancient art calledsteganography, which means covered writing. Steganography was originally used to hide secret messages so they could not be seen. Spies

sed the technique to hide secret information within innocent documents, such as books or letters, in order to move information past an enemy without detection. Invisible ink is one example of

a steganographic process.

When applied to a digital image, the process used is known as watermarking. Watermarking takes its name from the world of paper and ink. Currency has a watermark to prevent counterfeiting.Fine writing papers use watermarks to identify the manufacturer and build brand loyalty. A watermark is synonymous with quality and integrity. Digital watermarks are generally used for one of

hree purposesdata monitoring, copyright protection, and data authentication. Digital watermarking can be either visible or invisible to the viewer. A visible watermark is primarily designed to

display a copyright notice, telling the viewer who owns the image rights. An invisible watermark can also be used to assert a copyright, but it is designed to catch those persons who would try to

infringe on the copyright by using the image without permission of the owner. Watermarks can also be used to authenticate the integrity of an image. When used for this purpose, a software

rogram is used to calculate a unique number using the image data. To establish specific ownership of the image, an encryption key assigned to the owner of the image can be used to encrypt the

nique number generated from the image. The encrypted number is then inserted, by various methods, into the image itself. If ownership is not important, then only the unencrypted value is

sed. Though the actual techniques used are complex and vary from one manufacturer to another, the process of inserting this value into the image alters the image data. Some techniques can

introduce frequency distortions or other types of degradations that are visible to the human eye (Kutter and Petitcolas 1999). A number of papers have been published that describe a number of

echniques that can be used to remove or disable digital watermarks (Petitcolas, Anderson, and Markus 1998; Johnson 1999). Software tools such as Stirmark(Version 3.1) or unZign

(Version 1) are specifically designed to scan images for watermarks and remove them.

Watermarking and encryption may seem like good answers for those who would question the integrity of an image. When these processes change the original image data, however, answers to

questions such as Isthis image in the same condition as when it was originally captured?become clouded with doubt. Visible or not, the image was altered and, at the very least, every piece ofsoftware that touched that image is going to be subject to examination. A claim could be made that the enhancement process is valid, but because the image was contaminated by the

atermarking or encryption process, any conclusions based upon a contaminatedimage are suspect. An affirmative defense against such a claim would have to show that the watermarking or

encryption process did not affect the results obtained. To do that, it would be necessary to repeat the enhancement process on a cleanversion of the same image. A comparison could then be

ade to determine whether the encryption or watermarking process influenced the results of the enhancement process. Should it be determined that there is little or no influence, the next logical

questions would be: Is this result unique to this image or does it hold true for any image? What is the error rate? Can this be calculated? In this scenario the availability of a clean version of the

image in question was assumed. Where did it come from? It is unlikely that any system using encryption or watermarking is going to maintain a second copy. Not only would this double storage

space requirements, it would create difficulties if not impossibilities in the authentication and tracking of the second copy, which was not watermarked or encrypted.


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Agencies contemplating the use of any system that will alter the original image, whether for authentication purposes or to save storage space, would be well advised to run tests. At a minimum,

esting should be done to determine any potential effects watermarking or any other alteration might have on enhancement processes. A sufficient number of tests should be run to determine

hether there is a measurable error rate as a result of the alteration. In other words, can the same image be consistently captured, processed by the system in question, and then enhanced, with

he result being the same as those obtained from a cleanimage? If not, how often do the results differ? Why? What happens when the same series of tests are run on different images? Is the

error rate, if there is one, the same? In the case of images that are used for analysis purposes, such as fingerprints, are there any artifacts or false minutiae in the altered image that did not appear

in the clean image? Answers to these questions will go a long way toward building an affirmative defense in court, should the issues be raised.

An effective image-handling system should be able to track the chain of custody and ensure image integrity without having to alter original image data. Systems that rely on a watermark or

similar process that alters image data as part of the authentication process open the door to a myriad of questions that will only confound and confuse the average juror.Back to the top

Image Tampering

An issue that bears mentioning at this

oint is the potential for claims that an

image was intentionally altered to

implicate an otherwise innocent person.

The O. J. Simpson murder case (State of

California v. O. J. Simpson: acquitted of

urder charges, 1995; found liable in

subsequent civil trial for wrongful

death,1997) should serve as a warning to

hose who forget just how effective claims

of evidence tampering and planting of

alse evidence can be. Because digital

imaging is still relatively new to the legal

system in the United States, and because

ost juries have been exposed to digital

imaging in the form of television

entertainment, a claim of evidence

ampering has the potential to be quite

effective in those cases in which the chain

of custody is poorly documented.In December 1995, this issue was raised

riefly during a murder trial in Seattle,

Washington, in which a digitally enhancedalm print was the only conclusive

evidence that tied the defendant, Eric

Hayden, to the crime scene. The defense

aised questions about the ability of the

computer to make arbitrary changes to an

image without the knowledge or consent

of the operator. He implied deliberate

In the Eric Hayden case, Amido

Black

as used to enhance ridge detail in a

alm print found in blood on a bed

sheet. This process emphasized ridgedetail but stained the fabric blue

(top). Digital enhancement of the

alm print suppressed the fabric

ackground and improved image

contrast (bottom).


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changes could have been made to the

image, by the operator, which resulted in a

alse identification. The defendant claimed

he use of digital image processing

iolated the best evidence ruleand

questioned the acceptability of the

echnology by the scientific community.

The best evidence rule is more accuratelycalled the originaldocumentrule,

ecause it expresses a preference for

originals, and is the basis of Evidence

Rule 1001.Many in the photographic community

ave established rules for the use of digital

imaging within their disciplines. News

organizations in particular do not allow

any images that are used for documentary

urposes to be altered. Even images used

or editorial purposes are strictly

egulated. The credibility and integrity of

documentary images must be protected to

ensure their acceptance. Once the integrity

of an image becomes suspect, so too is the

subject portrayed.A bloody print (top) found

on a mattress pad was

rocessed with Amido

Black to darken the

ingerprint ridge details

and improve their visibility

against the fabric

ackground. A computer-

enhanced image of the

same print (bottom)

sharpened the contrast of

the fingerprint andemoved the fabric pattern

rom the background

(Warrick 1999).Several magazine and newspaper articles have been written over the past few years on the subject of image integrity and reliability. One article, written by a legal photographer in Boston,

Massachusetts, states: Itllbe very difficult with digital photography to prove beyond a reasonable doubt the authenticity of a photograph admitted into evidence(Silverman 1993). Another

article, published by the Wall Street Journal, describes how O. J. Simpson claimed, as part of a civil trial for wrongful death, that photographs of him wearing a pair of Bruno Maglishoes

ere fakes (Nelson 1997). The author, Emily Nelson, also highlighted several criminal cases where the defendant questioned the integrity of photographs.


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Law enforcement has only just begun to grapple with the issue of image integrity. There are no rules or standards to regulate the application of digital imaging. Agencies such as the Federal

Bureau of Investigation have formed study groups in an attempt to establish minimum guidelines, but so far these groups have concentrated on image quality and the associated hardware used to

capture images. Those who would use digital imaging to record objects or events that will later end up in court would be wise to consider these issues carefully. When the defense claims an

image was altered, it will be the prosecution that has to prove it is not so. Adequate documentation is a good place to start, but specific knowledge about digital images, how they are created, and

ow they can be changed, must be learned through training and practice. Policies and procedures establish how and when digital imaging will be applied. They also demonstrate to the defense

hat an agency stands behind the use of digital imaging as a tool. When followed, policies and procedures can also serve to reinforce the testimony of those who must defend its use in court.

When they are not followed, or when there are no established policies or procedures, the witness is left to him or herself against a group of people who are paid to find fault, no matter how small

or insignificant.Back to the top

Conclusion

There is little doubt that, over time, digital imaging will replace film as the preferred method for recording crime scenes and the evidence found in them. How the American legal system adjusts

o this technology is yet to be seen. History has demonstrated time and again that American jurisprudence adjusts to new methods slowly and deliberately. The American courtroom was modeled

after early nineteenth century English courtrooms that were designed to cast a defendantsaccusers as actors in a stage production that frequently resembled the latest plot in a modern soap

opera. The attorneys produce the show, and a judge ensures everyone plays his or her part according to the rules. This description might seem trite to some, but recognizing the similarities

etween a legal battle and a Broadway play can help an expert witness to better understand his or her role and how to play that role effectively.

The American system of justice is not known for its expedience. American legal tradition demands that any deviation from historical precedent be considered carefully. New case law is not

something most judges seek to create. How the courts will ultimately address the issues raised here must, for now, remain an educated guess. In the end, when an image is introduced in court, the

irst question that will need to be answered remains, Isthis image a fair and accurate representation of the scene or object as it was found?Questions about chain of custody or the validity of

specific computer enhancement techniques will ultimately be answered in accordance with the recognized scientific principles of the day.

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Legal Ramifications of Digital Imaging in Law Enforcement

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