Forensic Audio and Video Analysis

In most cases, the goal of the forensic audio or video professional is to provide the absolute best representation possible of the video or audio evidence. Low-lit video might be enhanced to provide more details, and muffled audio may be clarified so that the words are intelligible. However, each circumstance and recording is unique. While some dramatic improvements in clarity are possible, the results of a forensic audio or video exam are highly dependent on the quality of the source material.

Enhancement of video and audio are limited by the resolution of the original recorded image. For video recordings, the higher the pixel count or resolution of the image, the more detail is present in an image. A recording may depict a suspect walking across the crime scene, but if the camera optics are poor and the digital video recorder’s resolution was reduced, then zooming into the image may not provide additional details of the perpetrator’s appearance. The information was simply not recorded in the detail necessary to improve it. The configuration of the CCTV system and placement of the cameras is also imperative.

Common limiting factors include low light conditions for video recordings or noisy environments for audio recordings. Damage to the video or audio recording equipment can sometimes be compensated for; however, this varies widely by circumstance.

As with all forensic science disciplines, forensic laboratories, law enforcement agencies and private agencies put in place policies and procedures that govern facilities and equipment, methods and procedures, and analyst qualifications and training. Depending on the state in which it operates, a crime laboratory may be required to achieve accreditation to verify that it meets quality standards. There are two internationally recognized accrediting programs in the U.S. that are focused on forensic laboratories: The American Society of Crime Laboratory Directors Laboratory Accreditation Board and ANSI-ASQ National Accreditation Board / FQS

The Scientific Working Group on Digital Evidence (SWGDE) and the Scientific Working Group on Imaging Technology (SWGIT) each publish best practices and guidelines for ensuring quality and consistency across digital and multimedia examinations. They also incorporate best practice guidelines for managers, supervisors and quality assurance managers.

A report of findings is usually provided to the investigator or person who submitted the evidence for examination. The examination report may provide the following details:

• The nature of the request
• The results that were obtained
• Identification of the format/type of audio/video
• The type of processing that was performed
• Dates and time stamps that were visible
• Description of the subjects, if visible
• Description of the final product provided (e.g., enhanced video prints or video recording)
• Limitations in the examination

Not all audio or video evidence can be enhanced to provide clear details. While enhancements of recorded audio/video evidence can be made, those depicted on television crime dramas are often unrealistic. The amount of resolution required for the extreme magnification used in these shows usually is not recorded with cell phone or CCTV recordings.