Audio as Evidence
Written by Richard Brent   

Remember this phrase: “You’re innocent until proven guilty.” This expression is repeated over and over again in the U.S. during every criminal trial and represents one of the defining characteristics in our legal system. Many methods are used to gather information supporting a person’s innocence or guilt—evidence including video footage and personal testimonials. However, there is one type of evidence that is often forgotten: audio.

How many times have police reviewed tapes of people fighting and wished they could hear what was happening and who instigated the conflict? Did the combatants say names? On how many occasions have the accused stood in court wishing they had more than just the word of a witness to authenticate what happened? The reality is both audio and video are valuable to piece together all the facts in a story.

The main benefit audio provides to law enforcement and security officers is additional evidence. A clear, consistent audio recording can help a dispatch officer verify whether the alarm that sounded from the local convenience store was a false alarm or the beginning of an inappropriate incident. Additionally, live audio monitoring can assist law enforcement professionals in determining threats and preventing incidents, particularly at correctional facilities.

Audio in Correctional Facilities

Consider this hypothetical situation: Someone is smuggling suspicious packages over a detention facility’s perimeter. As the perpetrator approaches the facility (which has a security system with two-way audio speakerphones and IP cameras), a central station guard hears and sees the suspicious person approaching the facility on the monitor. Before the suspect makes another move, the security officer broadcasts to the invader saying, “You in the orange shirt! Put your hands up. The authorities are on their way. You have 12 seconds.” Not wanting to risk getting apprehended, the perpetrator complies, makes no sudden movements, and does nothing with the package. Two-way audio allowed the central station guard to alert the trespasser that he was being listened to, watched, and that security officers were on their way. The information and real-time interdiction was enough to stop him from going through with his original plan. The added security prevented a breach.

Live audio monitoring assists prison officers in defusing conflicts as the incidents occur. For example, guards can monitor inmates’ interactions on the jail floor from their control room when the audio and video surveillance technology is set up. If the officers hear the inmates are getting rowdy, they can broadcast over the talk-listen technology, telling them to settle down, warning them of the consequences, and mitigating any tension before a fight breaks out.

Audio certainly allows law enforcement to take a proactive stance on crime. It also provides key information for crime investigators and analysts. When it comes to gathering evidence in jail facilities, perhaps no other room carries the high level of importance as the interview room. Many detention facilities are moving to install high-quality microphones in their interrogation rooms—microphones powerful enough to catch a suspect’s quietest comments. Microphones that have mute capability are also popular because they allow someone to speak to their lawyer in the interrogation room while guaranteeing their conversation will be private.

Audio is also used in court of law, providing an oral record—in addition to the court stenographer’s transcript—of all court procedures. Audio capture and recordings, which are downloaded from microphones connected to DVRs or IP cameras, also contribute to delivering evidence substantiating that the police officer, suspect, or witness was following protocol.

Capturing Sound Evidence

Successfully capturing audio evidence starts with making sure the right audio solution is selected and installed. Here is a list of best practices:

1) Select the Audio Product.

  • To determine the best audio product for your application, consider questions like:
  • What features are essential for the audio product for this application? Live listening and recording? Recording only? Listen-talkback and recording?
  • Will the microphone be installed indoors or outdoors?
  • If the microphone is installed indoors, how small or large is the pick-up area? What is the size of the room, the composition of the walls (concrete, wallboard, etc.), and conditions of use?
  • If the microphone is installed outdoors, will it need to endure extreme weather conditions?
  • The answers to these questions and a few more will determine the technology, and the size and type of housing for the microphone. This will aid in selecting complementary equipment, as well as where the microphone is installed.

2) Conduct a Site Assessment.

Have your trusted advisor and security integrator scope out the site location to select the best areas for microphone placement. Do this ahead of time. An analysis of the location before installation day allows the technician to avoid installing products near air conditioning vents, laundry rooms, and other areas with unnecessary ambient noises.

3) Set up the Audio Solution.

Following the site assessment, the technician can install the microphone and connect it to the security network. For some applications, there may already be a camera in place that has audio capability. If that’s the case, the integrator just needs to configure the audio component, which is done through the video management software.

4) Test the Sound.

After the microphone is connected, test the sound. If the sound quality is a little distorted, it may be because the microphone output is line level while the camera’s input is mic level. To fix the problem, simply adjust the camera setting to accept line level input in the software. If the sound still needs to be finessed, adjust the gain stages on the preamplifier or camera.

5) Post Clearly Visible Signage.

For the final step of installation, put up a clearly visible sign or decal that communicates that monitoring is taking place in the environment. The sign is critically important as it identifies to people that they’re in a public place where there should not be an expectation of privacy. Most statutes state that as long as one manages the expectation of privacy, it is legal to monitor. For more specific situations, such as recording a conversation in a room among a group of people, refer to each individual state’s policy. All states have a slightly different policy on the expectation of privacy, managing that expectation and even the number of parties that need to give consent for the monitoring to be acceptable. Consult your local attorney for more information.
By providing additional evidence, audio is a valuable tool for security and investigative staff. It’s also an effective yet simple way to upgrade a security surveillance system. In this age of instant communication and response, audio will play an increasingly important role in ensuring security and accountability for law officers.

About the Author

Prior to becoming CEO of Louroe Electronics—a domestic manufacturer of audio monitoring technology—Richard Brent worked for Caterpillar’s Solar Turbine, Inc. for over 24 years, the last 12 years of which were based in Washington, D.C. to manage federal and state government relations. Now, Brent’s organizational guidance has spurred Louroe Electronics technologies to participate in a wide range of domestic and international government security initiatives, medical research facilities, commercial A/V security systems, and law enforcement.

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