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Voice Biometrics Enhance Prison Calling Security

Written by James C. Lowery

Photograph By: Mikeal Karlsson/Alamy


Tracking and monitoring inmates within a prison or jail is a constant challenge, especially when it comes to overseeing their communication with the public.  Although frequent communication with an inmate’s support group is encouraged in order to improve the probability of successful community re-entry, there is still a large group of inmates that continue to commit crimes by utilizing the inmate telephones.  The safety of the community, correctional officers and the inmate population is at stake, and it is up to inmate communications providers to develop effective solutions to meet these continuing challenges.


The Basics of Tracking Inmate Calling


Detention facilities are legally required to track, record and monitor all calls made by inmates to prevent illegal activity and prosecute further criminal behavior. At most facilities, inmates are assigned a unique Personal Identification Number (PIN) which they are required to use when making calls.  


These PIN’s are used to track inmate calling patterns, identify call recordings and records, and manage inmate contacts.  As an example: an inmate incarcerated for raping someone would not be allowed to contact the victim by placing a contact restriction on that inmate’s PIN. 


Unfortunately, there is a population of inmates that “share” their PIN, either voluntarily or involuntarily, with other inmates. The sharing of PINs circumvent prison security regulations making it nearly impossible to accurately track who truly made the call.  PIN sharing would allow an inmate to make unregulated calls to inappropriate contacts, such as criminal associates outside of prison, to continue illegal activity or to threaten victims into not testifying.     


Voice Biometrics to Increase Prison Safety


Voice recognition is the area of biometrics in which auditory noise is examined in order to identify an individual.  One of the most extraordinary applications of voice biometrics is the identification of inmates when they make a call from prison.

Correctional voice biometrics are able to guarantee that the inmate placing a call is who they say they are. The system’s decision engine uses statistical pattern matching techniques, advanced classification methods, and inputs from multiple mathematical algorithms to properly verify and identify speech.

When an inmate enters a prison, the inmate provides a base voiceprint when they first attempt to make a call utilizing their PIN.  This voiceprint is then permanently linked to their PIN. The process of creating a voice print is called “enrollment”.   Voiceprints are not .WAV audio files and can’t be modified.  They are statistical representations of speech and thus cannot be stolen or used anywhere except within the inmate phone system.

Once an inmate has enrolled their voiceprint into the system they will be required to match their voiceprint to place all future calls.  If an inmate’s attempted voiceprint matches the voiceprint on file in the Inmate Registry, the call can proceed.

In the event the attempted voiceprint does not match the voiceprint on file, the inmate will be notified that the call cannot proceed.

In advanced voice biometric systems , if an inmate fails a voiceprint match, the system produces a report of attempted PINs that did not match voiceprints on file and sends a notification to investigators for a detailed inquiry into the detected PIN fraud.



One of the major drawbacks with voice biometrics in a correction environment is noise level within a prison that causes the inmate’s voice print to produce a false negative.  False negative results can cause facility operators to lower the voiceprint threshold level in an effort to eliminate the issues.  As a result, inmates are sometimes able to pass voice biometrics using another inmate’s PIN.


Enhanced Calling Security


To eliminate the drawbacks associated with voice biometrics technology, innovative companies like Legacy have developed enhanced call security solutions such as AccuPINTM.


AccuPIN is a Legacy-developed, fully enhanced service that helps protect inmates from sharing (or stealing) one another’s Personal Identification Number (PIN). 


This technology simply requires an inmate to verify his/her PIN number along with a set of personal challenge/response questions entered into the Jail Management System (JMS) at the time of booking. The combination of unique and personal data offers a Protection Profile equal to the National Institute of Standards and Technology Level-4 Security. 


The key to the method’s success is varying the data request that offers mechanisms for minimizing a compromise of credentials. Data sharing by inmates is eliminated by a rotating set of challenge questions; basic information yields a set of limitless questions and can be configured to the protection profile.


Variations in Voice Biometric and Call Security Services


The most significant differentiators in call security services are the developer of the service and the system’s controller. The optimal solution comes from an inmate communication provider that develops, updates, customizes and controls the solution internally. Partnering with a single source provider means detention facilities will always have the most updated version of the technology and can have a tailored solution to meet their needs. 


Outsourced solutions, such as inmate communication providers that purchase or partner with companies that provide voice biometrics, can initially provide passable solutions which typically fall behind in technology support and advancement due to the lack of system integration/control. This is due to the rapid improvements in the tech industry and the subcontracting company’s inability to keep up with the dynamics of a changing industry. 


So, when looking for a new inmate communications provider with advanced call security features for your detention facility, focus on a single source provider with an internal technology department.  


Let us know your thoughts on Voice Biometrics technology in prisons and detention facilities by leaving a comment below, or dropping us a line on Facebook or Google+.


About Legacy Inmate Communications

Legacy is a nationwide provider and has been a leader in the inmate communications industry for over 17 years, with headquarters in Cypress, California.  We provide favorable rates for friends and family, unparalleled customer service and a host of technology options that complement all parties involved in reducing inmate recidivism. Legacy is unique in that it is a single-source provider, researching, developing, building integration and implementing every aspect of its Inmate Telephone Systems and Video Visitation Systems.


Comments (2) -

  • Md. Anwar Hossain Chowdhury

    4/21/2016 11:12:31 AM | Reply

    The article is really impressive as it deals with new kinds of biometrics data, Voice Biometrics. But I'm not sure how much accuracy will be achieved through this system.

    however, from the learners point of view, there is a new idea for thinking.

  • Donne Rimes

    8/19/2016 5:41:38 PM | Reply

    Sounds to me like a way for government to track prisoners after release