• Polygraph Testing
  • Digital Voice Stress Testing
  • Pre-employment Testing
  • Periodic / Preventative Testing
  • Issue-specific Testing
  • Taking down Statements
  • Referral to investigators
  • Evidence in supporting a case
  • Court and CCMA testimony

Truth Verification Specialist

Contact Us Services

Contact us on 073 954 3034

Member of South African Polygraph and Voice Stress Associotion (SAPAVSA)

About Us

Willem Ebersohn

Polygraph and Voice Stress Examiner

I am qualified Forensic Psychophysiologist and an accredited member of the South African Polygraph and Voice Stress Association. I completed my Polygraph and Voice Stress Examiners course in 2012 at the Truth Verification Centre, POLYVSA Institute in the Western Cape. I have 22 years of police experience as an ex-police officer. During my time as a Police Officer I completed a course as a detective at the South African Police Detective Academy in Paarl and was an active Detective for 5 years where I investigated various crimes on a daily basis. I’m therefor familiar with investigative questioning techniques and procedures.

I was also trained as a Suicide and Hostage Negotiator and did this as a secondary task for 4 years.

Body language (the body’s unknowing response during situations or conversations) plays a big role in the detection of deception and the trained person can observe a person’s body response to such situations or conversations and detect deceptive behavior associated with lying which could if handled correctly result in a confession.

My back ground as a police officer and experience as a Detective and Negotiator together with Polygraph and Voice Stress Examiners training is an affective combination in Detection of Deception. The Truth Verification Specialist always aims to render a professional and quality service and to be impartial in exposing the truth.


The truth fears no questions

What is polygraph test?

truth-verification-polygraphsThe Polygraph and Voice Stress examination is used in conjunction with and not as a substitute for a thorough investigation. Forensic Psychophysiological evidence may be utilized, corroborate or refute statements, obtain additional investigative leads, narrow or focus criminal investigations, serve to screen candidates for placement in sensitive positions and to assist in internal investigations.

The most valuable aspect of the investigative use of Polygraph or Voice Stress Analysis is to exonerate the innocent implicated by circumstantial evidence.  Polygraph and Voice Stress testing is also very helpful when investigating matters involving multiple suspects by eliminating suspects and narrowing the focus of the investigation.

Regardless the circumstances in which Polygraph or Voice Stress Analysis is used the test result are not the sole basis on which decisions are made, Polygraph or Voice Stress Analysis results are used in conjunction with other screening or investigative methods.

Polygraph Methodology

truth-verification-polygraphsWhen answering particular questions changes in the body occurs. These physiological changes are recorded and interpreted by the Polygraph. These changes are the result of messages received through the Autonomic nervous system. “Autonomic” means automatic or involuntary, so it deals with those aspects of the body that cannot be controlled voluntarily. The individual examined is unable to control those reactions in the body.

The Polygraph instrument records these Physiological responses through four sensors. If you tell the truth you will function at you normal Physiological level. If you are asked a question to which you are going to lie, your brain will register a “threat” because you do not want to be caught in a lie. As soon as your brain registers the threat your body automatically shifts into fight or flight response.

During the Polygraph examination the threat is associated with being caught in a lie because of the possible consequences. Because the individual does not have control over physiological responses the recording of these changes in the body by the Polygraph remains one of the most effective methods of establishing truthfulness.

Voice Stress Analysis Methodology

truth-verification-polygraphsVSA collects data from the voice. One of the physiological responses to lying is an involuntary tightening of mussels surrounding the larynx. The result is lowering of the frequency at which the subject’s voice normally oscillates. This oscillation has been termed the “Lippold Tremor”. The frequency lowering of the “Lippold Tremor” creates an unmistakable tracking. There is no way that the subject can manipulate the “Lippold Tremor”. “Playing” with the voice will make no difference. The subject is totally unable to manipulate the “Lippold Tremor”.

Unlike the Polygraph however the VSA does not require attachments. Since the Voice Micro-tremor is governed by the central nervous system and is graphically displayed in “real time” by VSA and instantly reacts to the psychological stimuli (the question) and instantly recovers to those stimuli, tests are not limited to questions as in traditional polygraph instrumentation.

The Polygraph and Voice Stress Analysis examination involves three Phases:

  • Pre-Test Phase
  • Data Collection Phase
  • Data Analysis Phase

Pre-Test Phase:

Paperwork will be completed and the examinee will be familiarized with the testing procedure and instruments. All Questions will be gone over with the examinee prior to being examined.

Data Collection Phase:

The examiner will administer the test and collect at least two charts recordings.

Data Analysis Phase:

The examiner will carefully review and scored each chart in order to render an opinion as to the truthfulness or honesty of the examinee’s answers.

Periodic maintenance testing

Periodic testing of personnel particularly in sensitive industries or instances where employees are placed in positions of trust that can easily be subverted and can be effective as a deterrent to aberrant behavior and acts as an early warning mechanism of potential risk.

Aside from permanent employees companies should insist on regular screening as a part of the service level agreement regarding outsourced staff and/or sub contracted companies (security officers, cleaners, maintenance ext.)

Testing intervals should be done depending on the amount of employees and timeframes determined by the employer/contract for example every 3 to 6 months.


Conducted prior to employing, possible candidates in order to eliminate those who had been involved with unidentified crimes or dishonesty and who would not be completely suitable for the available position.

Specific Issues

Tests are usually directed at the person’s direct involvement with a specific incident for example Fraud, Theft, Sabotage, Infidelity, Cheating, etc.

When is an employer/Individual permitted to use a Polygraph or Voice Stress Analysis?

  • Employee/person had access to the property which is the subject of investigation.
  • There is a reasonable suspicion that the employee/person was involved in the incident.
  • There has been economic loss or injury to the employees’ business/individuals personal belongings like theft.
  • Employer/individual is combating serious alcohol, illegal drugs or narcotics abuse and fraudulent behavior in the company or home.
  • The employer/individual is combating dishonesty in positions of Trust.
  • The employer/individual is combating deliberate falsification of documents and lies regarding the true identity of the people involved.


Polygraph and Voice Stress Analysis Tests:

Pricing is determined by type and complexity of the test. Final pricing will be determined after type of test, complexity of the test and needs of the client have been established.

Polygraph Testing: R650.00 (Includes: Consultation, Testing and Report)

Voice Stress Analysis: R600.00 (Includes: Consultation, Testing and Report)

Pricing for personal issues like, infidelity, dishonesty, accused of misconduct within a relationship or being wrongly accused of misconduct in the work place will be discussed with the client.

Discount will be determined by the amount of tests done and distance to be travelled. Any discount if applicable will be discussed with the client.


Travelling costs will be detemined by the amount of tests conducted and distance to be travelled. In some cases no travelling will be charged. To be discussed with the client.

Tel: 073 954 3034 / Fax: 086 776 9062

Willem Ebersohn - Ex-cop & Detective. Accredited Forensic Psychophysiologist.


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