Digital Patrol, Part 2 - Technology and Communications -

Digital Patrol, Part 2

How to get digital images admitted as evidence



Steve Ashley | From the January/February 2006 Issue Tuesday, January 31, 2006

Digital cameras might sound like a great idea for law enforcement use for many reasons, including no film to buy, store, process or waste; easy storage of images on a computer; and no need to produce expensive reprinted enlargements.

But, and it's a big but, what about image admissibility issues? It's possible defense attorneys will challenge your digital images as unreliable, implying that it's too easy to alter digital images and, therefore, the court shouldn't admit them into evidence.

Of course, challenges to evidence admissibility are nothing new. An entire body of court rules, both federal and state, as well as case law, has evolved to deal with the issue of admissibility. In fact, any defense attorney worth their fee will always consider challenges to evidence. In this regard, challenges to photos are to be expected, and digital photos are no exception.

The problem: Although the legal framework for determining evidence admissibility has evolved over centuries, and the guidelines for admissibility of photographic evidence have developed similarly over many decades, digital images remain relatively new. Serious questions arise as to whether the existing admissibility requirements can apply to this new thing: the digital photograph.

In Part One of this feature ("Digital Patrol," September/October 2005, p. 46), I reviewed the ways you can adapt digital photography to fit your law enforcement needs. Part Two tackles the issue of admissibility and offers guidelines to increase the likelihood your images will be admitted.

Digital is Different

While digital image prints may look the same as film prints, the development process of each is altogether different. A digital image is nothing more than a computer file, and all information captured by computers is binary in nature. This means that, at its most basic level, computer information is made up of a series of "bits." Each bit is actually a little switch that's either open (which equates to a digital value of 0) or closed (a digital value of 1). These digits (hence the term "digital") combine in many different ways to make up all the different types of data that computers manage. The data is gathered into files, and the way in which it's gathered will determine the file's format. Thus, data gathered in a certain way becomes a word-processing file, while data gathered in a different way becomes a digital-image file.

When you take a picture with a digital camera, light enters through the lens, just as it does in a traditional film camera. But the similarity ends there. The light photons strike a light-sensitive cell that converts them into a series of 1's and 0's, thereby digitizing the image, and the camera's electronics save the information in a file within the camera.

This process is significant because the rules of evidence have evolved to deal with analog data, such as documents and photographs, and not digital data. Digital cameras represent a relatively new way of creating evidence, and the images they produce pose a whole new set of questions for the courts to consider.

Rules of Evidence

Most officers are familiar with the basic rules of evidence; that is, they know what they must do to ensure evidence will be admitted. Officers realize they must take care with anything seized as evidence to preserve it in as close to its original state as possible. They know they must document the possession of each item from the moment it's found until the moment it arrives in court. They know this evidentiary chain must be complete, with no gaps, and that anyone and everyone who had possession of the evidence along the chain must be prepared to act as a witness and to testify under oath that the evidence was preserved during the time it was in their possession. In fact, they know that they, or the primary officer on the case, must also testify regarding the chain of evidence, and that the item presented in court is in fact the same item seized at the crime scene.

This process of evidence preservation is one of the first and most important things an officer learns, and it applies to photographs of evidence and of the scene, as well as physical items. Photos of the scene become evidentiary items themselves, subject to all the same requirements as if they were a knife, a rock or an item of clothing picked up on scene.

In our society, we tend to accept photographic evidence as representative of what it purports to show. Although most people realize traditional photos can be manipulated in a darkroom, generally they conclude it's not easy to do, and that unless the manipulator is highly skilled, it's almost impossible to alter a photograph in a way that cannot be detected. The courts recognize this, and a body of evidentiary law has sprung up around the fact that two primary things must be established for a photograph to be admissible: relevance and authenticity.

The first of these is usually a legal question, which holds little bearing on this discussion. The second, authenticity, is more problematic. While some courts have occasionally excluded traditional photos because they could not be authenticated, generally this is not the case as long as testimony shows the photo in question accurately portrays the scene it's intended to portray. In fact, it's not usually necessary for the photographer to testify as long as the chain of custody for the film remains intact and documented, and that someone who can reasonably be expected to know can testify on the authenticity of the depiction.

The courts also generally accept a print as admissible under the best-evidence rule, as opposed to requiring that the actual negative be introduced into evidence (the negative is usually considered a sort of "super original" that can be examined if necessary).


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Steve AshleySteve Ashley is a retired police officer, and an active trainer and risk manager. Contact him at


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