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Standards and Guidelines - Forensic Science Communications - January 2005

Standards and Guidelines - Forensic Science Communications - January 2005


Forensic Science Communications January 2005 &#8211 Volume 7 &#8211 Number 1
Standards and Guidelines

Recommendations and Guidelines
for Using Closed-Circuit Television
Security Systems in Commercial Institutions: Part 2

Scientific Working Group on Imaging Technology (SWGIT)

Version 2.1 July 22, 2004

7. Cameras

Cameras used in CCTV systems should adhere to the following recommendations:

7.1. Black-and-White Versus Color Cameras

Although black-and-white video cameras may provide better image resolution than color cameras, the information available in color images may provide important investigative information. Therefore, the choice of cameras is left to the commercial institution, dependent on the intended use of the recorded images.

7.2. Camera Detector Size

Video and digital cameras use detectors that come in a variety of sizes. Typical sizes are 1/4, 1/3, and 1/2 inches. The size of the detector will have a direct impact on the focal length of the camera lens. See Section 7.5 for further information.

7.3. Camera Resolution

In order to meet the Scientific Working Group on Imaging Technology guidelines, analog video cameras must have an output resolution of at least 400 horizontal lines. Digital video cameras must have an output resolution of at least 480 horizontal lines. Cameras that have higher resolutions are strongly recommended.

7.4. Camera Infrared Characteristics

The detectors used in black-and-white video cameras may be sensitive to a part of the infrared spectrum that is outside of the normal range of human visual perception. This can improve the ability of the camera to record in low-light situations.

Due to the fact that images acquired by infrared-sensitive cameras can make some dark clothing and other objects appear to be lighter than they actually are, it is recommended that infrared-sensitive cameras not be used to record scenes that are well-illuminated. Many cameras are equipped with filters that can mitigate this effect. This does not apply to most color cameras that normally contain an infrared barrier filter to block infrared light.

The use of infrared-sensitive cameras should be noted in the system documentation (see Section 9.1).

7.5. Lens, Focal Length, and Field-of-View

The selection of lenses will be dictated by the field-of-view to be covered by each camera, as well as by the size of the camera’s detector.

For cameras placed to record images at a point-of-customer transactions, such as a teller window (See Section 5.3), the area of interest (e.g., face, license plate) should cover approximately 15 percent or more of the camera’s field-of-view (based on the recommended minimum resolution found in Section 7.3). For an average human head that is six-inches wide, a three-foot-wide field-of-view will meet this guideline. For a license plate width of approximately 12 inches, a six-foot-wide field-of-view is sufficient.

The focal length necessary to achieve an approximately three-foot-wide field-of-view for a given detector size and camera-to-subject distance is provided in Table 3. The camera must be in focus at the position of this subject.

Table 3. Approximate Focal Length (in mm) Needed for Three-Foot-Wide Field-of-View

Distance to
subject (in feet

2 5 10 15 20 30
Detector size
1/4” 2.3 5.9 11.7 17.6 23.5 35.2
1/3” 3.1 7.8 15.7 23.5 31.3 47.0
1/2” 4.0 10.1 20.2 30.3 40.4 60.7
(Differences in the units used to describe these resolution recommendations are due to the differences in the industry standards used to describe these media.)
Cameras that provide overviews of interior and exterior locations should have their focal lengths selected so as to meet the field-of-view requirements of the facility. However, exit cameras should have sufficient depth-of-field to be in focus at distances of three feet and beyond to ensure that subjects exiting the facility will be in focus.

7.6. Exposure Control

Cameras should be equipped with automatic mechanisms to ensure proper exposure under varying lighting conditions. Such mechanisms include, but are not limited to, automatic gain circuitry, day/night sensor switching, and lenses with automatic iris functions.

7.7. Camera Housings

Cameras may require coverings and environmental controls to protect them from the elements or tampering. Clear coverings placed in front of camera lenses will reduce image quality; therefore, unless there are specific environmental or security concerns that require camera housings, it is recommended that they not be used.

8. Media

Media, including analog videotapes, compact discs, digital video tapes, and digital versatile disks, should be of high quality and meet equipment manufacturers’ specifications. Low-quality media can result in damaged equipment and poor images.

9. System Maintenance

CCTV systems should be maintained in a manner that ensures their proper function over their entire lifetime. Therefore, the following recommendations should be adhered to:

9.1. System Documentation

Institutions should maintain documentation regarding their CCTV systems that includes the following information:

    • Make and model of all system components, including recorders, cameras, lenses, and multiplexer/switcher. For digital systems, this information should include software and hardware information, including software version. If infrared-sensitive cameras are in use, their location should be documented. An example of a system information sheet is included in Appendix C. If possible, a photocopy of the maintenance record should be included.

    • Adequate system documentation should be included at the site. This includes instructions for downloading and outputting recordings.

    • Point-of-contact information for system installer and/or system maintenance organization, to include at least two names and telephone numbers.

  • Site plan showing all equipment placement (including recorders), as well as field-of-view for each camera. Appendix C includes an example of a site plan.

This information should be verified monthly and made available to responding law enforcement officials on their arrival at the scene.

9.2. System Validation and Maintenance

Prior to use, systems must be validated to meet the requirements of Section 4. The systems must be capable of acquiring, recording, and producing output images that are of sufficient quality to enable law enforcement officials to identify the people and objects depicted therein. Revalidation of these requirements must occur every time the system is altered.

A variety of system checks and maintenance are necessary at different times. If system errors are found, steps to correct them should be implemented.

A maintenance log must be maintained to document all system-validation activities, checks, and maintenance activities.

Table 4 provides a calendar for these checks and maintenance items that should be recorded on a maintenance log.

Follow this link to Table 4.

9.3. Maintenance of Recording Media

Institutional requirements will dictate the length of time for which recorded images must be archived.

All recording media has an expected usable life span. Based on that life span, policies should be developed to ensure that media is replaced before this period expires. For example, it is recommended that VHS video tapes be reused no more than 12 times and that they be replaced on an annual basis. This use of extended time-lapse mode may drastically shorten the life span.

For digital recording devices, manufacturer’s recommendations for maintenance and the device service-life replacement schedule should be observed. A regular ongoing (automated) inspection of hard drives should be conducted to ensure that the disk(s) is/are functioning properly and that there are no bad sectors or other hardware errors that could result in a loss of data. Other reusable media must be recertified no less frequently than the manufacturer’s guarantee period.

Institutions should establish policies regarding the marking of removable media so that the most recent date of recording will be documented.

10. Retention of Recordings

It is recommended that analog videotapes be retained for a minimum of 31 days before being reused. This coincides with the 12-time use recommendation. For ease of retrieval, each videotape should be sequentially numbered, and the dates and times recorded on each tape should be written on a label on the videotape.

Due to the nature of digital recordings, the Scientific Working Group on Imaging Technology recommends that recordings be retained for the longest time possible (minimum of 10 days) with the least amount of compression available in the system’s capabilities. Storage capacity to meet these needs must be

11. Evidence-Handling Procedures

This section addresses procedures to follow when law enforcement response is necessary. This may be in response to a robbery, or it may be related to other criminal investigation.

11.1. Documentation for Law Enforcement

The system documentation, as described in Section 9.1, including equipment information, site plan, contact information, and maintenance log, should be made available to responding law enforcement officials. Any additional pertinent information regarding the recording or the incident itself should be noted, such as incident time, record mode, and discrepancies between actual time and recorder time. Appendix C includes an example of documentation.

11.2. Handling Evidentiary Recordings

Following an incident involving immediate law enforcement response, it is necessary to ensure that the recorded images are secured. Unless the possibility exists that the images may be overrecorded or overwritten, the recording should not be stopped until law enforcement officials arrive.

11.2.1. Video-cassette tape systems

Upon terminating a recording, the tape should be removed from the recording device and the recording tab immediately removed or shifted to the record-disabled setting. The tape should not be played again prior to the arrival of law enforcement officials. The name of the institution and identity of the person performing this function should be marked on the exterior of the cassette housing, along with the time and date of removal.

Prior to transfer to law enforcement officials, steps must be taken to ensure that the tape is not mishandled or damaged. This includes keeping the tape away from magnetic fields, such as those generated by televisions, radios, and speakers. The tape should be maintained at room temperature and out of direct sunlight. Tapes should not be stored in vehicles for an extended period of time.

Personnel qualified to assist law enforcement in recovering images from the tape should be identified and made available prior to the arrival of law enforcement officials.

11.2.2. Digital video systems

The following steps should be followed:

  1. Upon terminating a recording, personnel qualified to assist law enforcement in recovering images from the CCTV system should be identified and made available (in person or by telephone) to offer technical assistance.
  2. Law enforcement officials will coordinate with appropriate personnel to view and retrieve the best image(s) prior to the officials’ departure from the crime scene. When immediate transmission of images is necessary to expedite distribution from the crime scene, the images should be transmitted by network, e-mail, compact disc, or other available means. Images shall be provided to law enforcement in the TIFF, BMP, or JFIF (JPG) formats. If the facility uses a remote location for the storage of recorded images, then the facility will provide the images to an address designated by the law enforcement officials.
  3. The facility’s security personnel will produce at least two copies of the relevant images and video on compact disc (CD) or digital versatile disk (DVD) (nonrewritable) in the nonproprietary formats as well as the original native format.
  4. In the event of alarm-trigger incidents as described in Section 6.8, law enforcement would like all video and relevant data that were recorded five minutes before the alarm-trigger, the entire incident, and five minutes after the incident. This is barring any outside circumstances when it is required to save a longer period of time (e.g., casing of the bank).
  5. If additional retrieval of video recording is warranted, law enforcement officials will notify the facility’s security personnel to secure the hard drive or retrieve additional video and data. The facility will be required to maintain all recorded video and data on a rolling ten-day period from the event of a crime. This means that at the date of the crime, law enforcement officials would be able to review all video for ten days prior to the crime. As an example, two days after the crime, law enforcement officials would be able to review all video for eight days prior to the crime and so on.
  6. When the relevant video, images, and data have been copied, each shall be labeled with the name of the institution and identity of the person performing this function, along with the time and date of removal. This information should not be written directly on the media but preferably on a label that is affixed to a protective container, such as a jewel case, sleeve, or clamshell enclosure.

Appendix A: References

Aldridge, J. CCTV Operational Requirements Manual Version 3.0. Police Scientific Development Branch, United Kingdom Home Office, Publication Number 17/94, 1994.

Aldridge, J. and Gilbert, C. Performance Testing CCTV Perimeter Surveillance Systems. Police Scientific Development Branch, United Kingdom Home Office, Publication Number 14/95, 1995.

Atkinson, D. J., Pietrasiewicz, V. J., and Junker, K. E. Video surveillance equipment selection and application guide, National Institute of Justice Guide 201-99. In: Law Enforcement and Corrections Standards and Testing Program, February 2000. Available:

Brown, B. Crime Reduction: Closed Circuit Television in Town Centres: Three Case Studies. United Kingdom Home Office Police Research Group. Crime Detection and Prevention Series. Publication Number 68, 1995. See https://www.ncjrs.gov/App/publications/abstract.aspx?ID=160337

Diffley, C. and Wallace, E. CCTV: Making it Work. Training Practices for CCTV Operators. Police Scientific Development Branch, United Kingdom Home Office, Publication Number 9/98, 1998.

Green, M. W. Appropriate and effective use of security technologies in U.S. schools. In: A Guide for Practical School Security Applications. September 1999. Available:

Griffiths, A. CCTV: Making It Work. Time and Date Displays. Police Scientific Development Branch, United Kingdom Home Office, Publication Number 13/98, 1998.

Mather, P. Guidelines for the Handling of Video Tape. Police Scientific Development Branch, United Kingdom Home Office, Publication Number 21/98, 1998.

Nichols, L. J. Use of CCTV/Video Cameras in Law Enforcement. International Association of Chiefs of Police. March 2001.

Police Scientific Development Branch. Digital Imaging Procedure Version 1.0. Police Scientific Development Branch, United Kingdom Home Office, Publication Number 02/2002, 2002.

Rason, J., Kent, T., Sall, I., Gugenheim, P., and Walker, S. Assessment of the ADVIS, IMPRESS, VIEW Video Enhancement System for the
UK Police Service.
Police Scientific Development Branch, United Kingdom Home Office, Publication Number 1/2000, 2000.

Scarman Centre National CCTV Evaluation Team, National Evaluation of CCTV: Early Findings on Scheme Implementation: Effective Practical Guide. United Kingdom Home Office Statistical Bulletin 5/03, 2003.

Security Industry Association, 1998-1999 CCTV for Public Safety Report, Security Industry Association, 1998.

Tilley, N. Crime Reduction: Understanding Public Car Parks, Crime and CCTV: Evaluation Lessons from Safer Cities, United Kingdom Home Office Police Research Group. Crime Prevention Unit Series Publication Number 42, 1993.

Wallace, E. and Diffley, C. CCTV: Making it Work: Guidance on Recruitment and Selection Practice for CCTV. Police Scientific Development Branch, United Kingdom Home Office, Publication Number 8/98, 1998.

Wallace, E. and Diffley, C. CCTV: Making it Work: CCTV Control Room Ergonomics. Police Scientific Development Branch, United Kingdom Home Office, Publication Number 14/98, 1998.

Appendix B: Technical Guidelines for Lighting

In this document, illuminance is measured in Lux. Some older documents and references may refer to the measurement in foot candles (one-foot candle is approximately equal to 11Lux).

To provide good-quality camera images, a minimum of 277 to 333Lux of illumination should be provided in the customer areas, office areas, hallways, stairways, and exits where there is camera coverage.

Exterior self-service facilities, such as automated teller machine vestibules or drive-up lanes, should have a minimum of 110Lux of illumination 24-hours daily to ensure good image quality.

Exterior areas, such as sidewalks, entrances, night depository areas, that have camera coverage should have a minimum of 55Lux of illumination.

Parking lots with camera coverage should have a minimum of 11Lux of illumination at ground level.

Supplementary surface lighting may be necessary for adequate illumination for the face of anyone using an automated teller machine or other self-service resource.

Appendix C: System Documentation and Site Plan Examples

System Equipment Information
Recorder make and model________________________________________________________
Multiplexer make and model_______________________________________________________
Camera/s make and model _______________________________________________________
Are any cameras infrared-sensitive and if so identify_________________________________
Video format (circle) VHS SVHS DVR PC
If DVR or PC-based:
Hardware manufacturer_____________________________________________________
Software name and version___________________________________________
Is a copy of the most current maintenance/service log attached?
(circle) YES NO
Does the system record multiple cameras? (circle) YES NO
If yes, how many?___________________________________________________

Contact Information

Recording system point of contact _______________________________________
Telephone: ____________________________________________________________
Institution point of contact ______________________________________________
Telephone: ___________________________________________________________

If the system records multiple cameras, note the camera location and angle view. Use the following diagrams as examples.


Include the following additional information in the event of a law enforcement response:

What record mode was the system? (circle) 2 hour, 6 hour, 12 hour,
24 hour, 48 hour, 72 hour,
Does the recorded date/time accurately represent the time of day?
(circle) YES NO
Date and time of incident
Date and time of incident on tape______________________________________________
Date and time recording removed from equipment
Other Information:

Picture of Example of Site Plan for Small Bank

Camera 1: Teller one, facing east
Camera 2: Teller two, facing east
Camera 3: Teller three, facing east
Camera 4: Teller four, facing south
Camera 5: Teller five, facing south
Camera 6: Customer-service area, facing south-west
Camera 7: Customer-service area, facing north-west
Camera 8: Lobby, facing north-west
Camera 9: Lobby automated teller machine one
Camera 10: Lobby automated teller machine two
Camera 11: Emergency exit, facing west
Camera 12: Parking lot, south side of building
Camera 13: Parking lot, south-east corner of building
Camera 14: Drive-through service lane, facing west
Camera 15: Drive-through service lane, facing south


Picture of Example of Site Plan for Convenience Store

Camera 1: Clerk and check-out area, facing east
Camera 2: Front door entrance, facing north
Camera 3: Outside of office, facing south
Camera 4: Freezer area, facing south
Camera 5: Emergency exit, facing south
Camera 6: Automated teller machine, facing west
Camera 7: Parking lot, facing south-east



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