Facing CSI Data Storage Overload?

Posted on October 24, 2011

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By Houston Thomas, CDW Government

A few decades ago, the number of photos taken at a given crime scene may have been limited due to the expense and time associated with film processing. That is not the case today. The cost for law enforcement agencies to capture still images, video and audio has decreased significantly, and as a result, the amount of evidentiary data gathered continues to grow.  Video from patrol cars, surveillance systems and interview room applications add volumes of data to evidence management repositories.

The investment required for digital evidence capture devices has been on the decrease for some time now. Many of today’s smartphones include a camera that can record audio as well as photos and video. These new devices enable camera-equipped citizen journalists to take additional photos and videos that may be beneficial to an investigation. 

The additional digital evidence is a boon for law enforcement professionals. But the increased volume of evidence comes with its own set of challenges – most importantly, the need to develop processes for managing, storing and securing data effectively.

Managing digital evidence

Upon receiving digital evidence, law enforcement agencies must properly track and maintain a “chain of custody.” Video files, still images and audio files created or gathered by agencies for an evidentiary purpose should be controlled in the same way that the agency controls physical evidence, with similar policies and procedures for chain of custody.

Court challenges to the validity of data are of concern, making the ability to properly manage the original file imperative. Cameras and audio equipment are available today that can apply a digital fingerprint to an original file. These types of marking systems, along with comprehensive notes from an investigator, will show that the original file has not been altered and that any enhancement techniques were performed using an exact copy of the original file.  Video files use coding algorithms that ensure on a frame-by-frame basis that the video has not been altered.

Data loss is a particular concern when exporting video from a data collection device. Most video capture systems export in a compressed format, which may cause some data loss. Any conversion process must be addressed in an organization’s standard operating procedures and followed precisely. The procedures must indicate how files will be managed and verify that the process has been tested and validated to cause zero data loss. 

Another concern is leakage of video evidence to television news programs or Web outlets such as YouTube and Facebook. Software applications with role-based security features can ensure that only those authorized to delete, publish or share evidentiary files may do so. These applications also provide an audit trail that can be used for chain of custody reporting.

Storing digital evidence

Digital storage costs have been dropping in price each year as well, making digital media storage an increasingly viable solution for departments facing budgetary and physical storage constraints.

Agencies should consider several factors when selecting storage media devices, such as security and durability features.  SDHC (Secure Digital High Capacity) and SDXC (Secure Digital Extended Capacity) cards are in high demand for use to support storage of video and still images. New SD Worm technology or  Write Once, Read Many cards are tamperproof, making them useful for storing unalterable, permanent photographic records. Solid-state hard drives (SSDs) have no moving parts, making them more rugged and less susceptible to shock, vibration and extreme environments.

The size of the public safety department and amount of data being stored should also be a factor. For example, network-attached storage (NAS) is better suited for smaller departments in which all storage devices have dedicated IP addresses, while a storage area network (SAN) is an enterprise option generally seen in larger departments because it allows for higher-speed performance and can easily handle more data.

Storage system plans should employ both short- and long-term archiving systems.  Organizations may want to rotate infrequently accessed data to less-expensive types of storage, such as tape. Offsite backup is critical to ensure data is not lost in the event of a network failure or disaster such as a fire. As technology advances, law enforcement professionals should periodically assess the effectiveness and capacity of their data storage systems.

Securing digital evidence

Strong physical protection and cyber security are crucial to safeguarding digital evidence. Just as law enforcement organizations store physical evidence in a locked room and paper files in a locked container, systems containing image files should be separate from the department’s normal production network. Law enforcement facilities should monitor who comes and goes into secure areas of the building containing evidence. Additionally, permissions such as password protection should be in place so that even support personnel cannot access evidence files without permission, logging and supervision.

Any outside workers coming on site to repair computers, including government staff, must be vetted and then supervised while they access the system so that they do not inadvertently download or mistakenly damage evidence files. Passwords and encryption should be used as an additional layer of security for extra-sensitive data.

Where to go for help

The Scientific Working Group on Imaging Technology (SWGIT) is a great resource for digital evidence management guidelines and processes. The Law Enforcement & Emergency Services Video Association (LEVA) is a useful resource for training and information, including a technical database to assist in selecting video equipment.  The National Technical Investigators’ Association (NATIA) is also a valuable resource. The organization hosts an annual national training conference and technology exhibition showcasing a broad variety of surveillance and investigative support products.

Houston Thomas is a public safety solution architect at CDW Government (CDW-G), a leading source of IT solutions to governments and educators.


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