Sunday, 13 April 2008

Nothing But The Truth

“I swear by Almighty God that the evidence I shall give shall be the truth, the whole truth and nothing but the truth.”

English / Welsh Oath

The face says it all - I passed !

As arranged, Don Cargill arrived at my home at 3 o’clock. We sat over a coffee whilst Don talked about his life, qualifications and the many cases that he had handled. He highlighted his recent work with Michael Shields and the support that he had received from Rt. Hon. Jack Straw M.P., Secretary of State for Justice.

After a while, he assembled the polygraph equipment and explained the purpose of each component – the pneumographs, skin galvanic sensors and the cardiosphygmograph. Later he showed me examples of polygraph results, including Michael Shields’ test graphs.

For the next hour or so, we discussed the allegations that had been made against me. A typical polygraph test comprises three questions that will be examined and a range of other unrelated control questions for reference purposes.

In the end, the three questions were :
  • “Did you smack the girl on the hand on 26 September 2007 ?”
  • “Have you ever purposely hurt any child whilst working at your school ?”
  • “Were you sitting on a child’s green chair when the alleged smack on the girl took place ?”
Don then wired me with all of the polygraph sensors. After some preliminary tests / questions and calibration, everything was ready for my examination to start.

I was so apprehensive and scared. I can not describe my sense of anxiety ... it is the same feeling that you might experience when passing through the ‘Green Channel’ at an airport customs when you have nothing to declare; but this was much more intense.

He asked me to try to relax and to look directly ahead through the window as he began his questions. He asked me a total of six questions and this sequence was repeated three times.

After what seemed an eternity, he looked over at me and told me that I had answered truthfully to all questions.

He then showed me the graphs of my tests and how he had interpreted the various traces.

By this time, I was just so elated to know that I had proved my innocence – I HAD PASSED !



Example LX4000 Polygraph Traces
by courtesy of Lafayette Instrument Company



LX4000 Polygraph Components
by courtesy of Lafayette Instrument Company

The modern polygraph uses specialist software, LXSoftware (LX4000) & PolyScore, on a conventional Windows™ PC or laptop computer. Relative physiological changes within the examinee’s body are monitored by the following polygraph attachments :
  • Respiratory Rate : Two rubber tubes filled with air, called pneumographs, are placed around the examinee’s chest and abdomen. When the chest or abdominal muscles expand, the air inside the tubes is displaced. The digital or computerized polygraph employs transducers to convert the energy of the displaced air into electronic signals.

  • Galvanic Skin Resistance : This is also called electro-dermal activity and is basically a measure of sweat on your fingertips. The fingertips are one of the most porous areas on the body and therefore are a good place to look for sweat. The theory is we sweat more when we are placed under stress. Fingerplates, called galvanometers, are attached to two of the examinee’s fingers. These plates measure the skin’s ability to conduct electricity. When the skin is hydrated (as with sweat), it conducts electricity much more easily that when it is dry.

  • Blood Pressure / Heart Rate : A blood pressure cuff, called a cardiosphygmograph, is placed around the examinee’s upper arm. Tubing runs from the cuff to the polygraph. Again, in digital or computerized polygraphs, these changes are converted into electrical signals by transducers.
There are other components that a polygraph examiner might use, including a specialist chair, video camera and a range of sensor pads to detect countermeasures that might otherwise compromise the polygraph test results.

The polygraph examination involves three phases : The pre-test phase, the data collection phase and the data analysis phase.

In the pre-test phase the polygraph examiner will complete the required paperwork and then familiarize the examinee with the testing procedure and the polygraph instrument. He will spend most of the pre-test phase discussing the issue for the polygraph test. Before the examinee is attached to the polygraph instrument the examiner will review each polygraph test question with him, word for word. There are no surprise or trick test questions.

During the data collection phase the examiner will administer the polygraph test and collect a number of polygraph charts depicting physiological changes occurring with the examinee’s body as the examiner reads each test question and the examinee answers “yes” or “no”.

During the data analysis phase, the examiner will carefully review and score each chart in order to render an opinion as to the truthfulness of the examinee’s answers. The opinion rendered will be one of the following : NO DECEPTION INDICATED meaning the examinee answered the relevant questions truthfully, DECEPTION INDICATED meaning the examinee did not tell the truth to the relevant test questions or sometimes the opinion is inconclusive when the examiner is unable to determine truth or deception from the examinee’s polygraph charts due to abnormal and / or inconsistent physiological reactions.



The main supplier of polygraph systems and accessories is an American company, Lafayette Instrument Company, based in Lafayette, Indiana. The company was established in 1947 by Max Wastl.

Lafayette Instrument Company : www.lafayettepolygraph.com

Another polygraph systems supplier, again American, is :

Limestone Technologies : www.limestonetech.com



During my examination, I was asked to deliberately lie by reading from a prewritten script. It got very confusing as I had not appreciated that the lie was implicit in the script and I kept adding mine.

I came across this transcription involving an American witness who also suffered similar confusion whilst attempting to swear an oath :
Clerk:Please repeat after me : “I swear by Almighty God ...”
Witness:I swear by Almighty God.
Clerk:That the evidence that I give ...
Witness:That’s right.
Clerk:Repeat it.
Witness:Repeat it.
Clerk:No ! Repeat what I said.
Witness:What you said when ?
Clerk:“That the evidence that I give ...”
Witness:That the evidence that I give.
Clerk:Shall be the truth and ...
Witness:It will, and nothing but the truth !
Clerk:Please, just repeat after me : “Shall be the truth and ...”
Witness:I’m not a scholar, you know !
Clerk:We can appreciate that. Just repeat after me : “Shall be the truth and ...”
Witness: Shall be the truth and.
Clerk:Say : “Nothing”.
Witness:Okay. (Witness remains silent)
Clerk:No ! Don’t say nothing. Say : “Nothing but the truth ...”
Witness:Yes.
Clerk:Can’t you say : “Nothing but the truth ...” ?
Witness:Yes.
Clerk:Well ? Do so.
Witness:You’re confusing me.
Clerk:Just say : “Nothing but the truth ...”. Yes ?
Witness:Okay. I understand.
Clerk:Then say it.
Witness:What ?
Clerk:“Nothing but the truth ...”
Witness:But I do ! That’s just it.
Clerk:You must say : “Nothing but the truth...”
Witness:I WILL say nothing but the truth !
Clerk:Please, just repeat these four words : “Nothing”, “But”, “The”, “Truth”.
Witness:What ? You mean, like, now ?
Clerk:Yes ! Now. Please. Just say those four words.
Witness:Nothing. But. The. Truth.
Clerk:Thank you.
Witness:I’m just not a scholar.



I felt elated at the end of the day. I had been so apprehensive about my test. It had been more stressful and demanding than I had expected and it had been worse than the police interview last October. I had passed and, for the first time in months, I had new hope and a sense of contentment.

I thought that you might like to share my rekindled sense of fun with another courtroom transcription :
Lawyer:Doctor, before you performed the autopsy, did you check for a pulse ?
Witness:No.
Lawyer:Did you check for blood pressure ?
Witness:No.
Lawyer:Did you check for breathing ?
Witness:No.
Lawyer:So, then it is possible that the patient was alive when you began the autopsy ?
Witness:No.
Lawyer:How can you be so sure, Doctor ?
Witness:Because his brain was sitting on my desk in a jar.
Lawyer:But could the patient have still been alive nevertheless ?
Witness:It is possible that he could have been alive and practising law somewhere.

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