Wednesday, October 1, 2008

Polygraph Questions And Answers With Legal Pub

Reader: Legal Pub, You have tried many jury trials. How is it that you have developed a knack for deciding whether a witness is telling the truth?

Legal Pub: First, thanks for the question. Second, contrary to popular belief, lawyers do not always know whether a witness is telling the truth unless they have impeachment evidence available for contradiction. Impeachment evidence in the form of prior statements or physical evidence is demonstrative evidence of fabrication. Without such concrete evidence, the discussion turns to nonverbal communication which is not always reliable.

The first nonverbal signs often discussed in criminal cases is polygraphs. Unfortunately, the polygraph is not as reliable as many people think. The so called lie detector test measures nonverbal signals such as increased perspiration, increased heart rate, blood pressure, changes in respiration, voice inflection, and/or skin conductivity to identify signs consistent with fabrication. Some polygraphs now measure changes in the pupil thought to correspond with not telling the truth. Other non verbal signs include failure of the witness to look the cross examiner in the eyes. Pupil dilation may also give a clue to the veracity of ones statement. However, like a polygraph, the reliability of such findings is questionable.

Reader: How reliable are polygraphs?

Legal Pub: In my view, they are not reliable and a client should not submit to a lie detector test even if he is innocent because scientific data calls into question the reliability of polygraphs. ("Scientific Validity of Polygraph Testing: A Research Review and Evaluation". Washington, D. C.: U.S. Congress Office of Technology Assessment (1983). ) Advocates may argue that the test is 90% - 95% reliable, but too often the polygraph is just a means to launch an aggressive interrogation. In 1997, 421 psychologists concluded that the accuracy of polygraphs is about 61%. (USA Today LINK).

Our Supreme Court in United States v. Scheffer, concluded: “There is simply no consensus that polygraph evidence is reliable” and “Unlike other expert witnesses who testify about factual matters outside the jurors' knowledge, such as the analysis of fingerprints, ballistics, or DNA found at a crime scene, a polygraph expert can supply the jury only with another opinion...”. An Also, in 2005 the 11th Circuit Court of Appeals stated that “polygraphy did not enjoy general acceptance from the scientific community."United States v. Henderson (May 23 2005).

False positives on innocent people remains a genuine concern. .William G. Iacono, from the University of Minnesota, published a paper titled “Forensic “Lie Detection": Procedures Without Scientific Basis” which concludes that polygraphs may be useful as a tool to induce confessions; however, it not a scientifically credible test.

Polygraph testimony can be admitted by stipulation in many states. Daubert v. Merrell Dow Pharmaceuticals (1993) provides the standard for admitting such evidence if the "underlying reasoning or methodology is scientifically valid and properly can be applied to the facts at issue." Currently no state can force a defendant or witness to undergo a polygraph. In Massachusetts, Maryland, New Jersey, Delaware and Iowa an employer may not require a polygraph either as conditions to gain employment or as a condition to remain employed. The Employee Polygraph Protection Act of 1988 (EPPA) is generally in accord.

Reader: So what is a lawyer to do?

Legal Pub: Ultimately, the real finder of truth is a jury or judge.


pops said...

Good explanation. I would not want to take a lie detector test even if I was not even in the same state as where the crime occurred!


blond bombshell said...

Learning to tell when a man is lieing is so simple...

All you have to do is see if his lips move!


katfish said...

Do you feel one should never take a polygraph under any circumstances?
I keep thinking about Mark Klaas saying that was the first thing he did to move the investigation off of himself and towards the real perp.
Just asking. Love this blog!

Ms Calabaza said...

great post. I've been told the same by friends in law enforcement and law "don't ever take a polygraph".

Shell, you are spot on girlfriend!

Politely Asking said...

Joel Brodsky sure effed that up then didn't he?

Excerpt from letter from McCord and Associates (polygraph examiner):

"On May 25, 2008, Drew Peterson voluntarily submitted to a polygraph examination at the request of his Attorney Joel Brodsky of Brodsky and Odeh."

Legal Pub said...

The strategy of lawyers may vary. Sometimes a lawyer will ask his client to submit to a private lie detector tests to see if he will pass. This is done more as a measure of the clients demeanor then it is for determining veracity.

I have not discussed the polygraph with J. Brodsky so I do not know the circumstances of Drew Peterson taking a polygraph. Perhaps that can be a subject for a future interview.

Thanks katfish. I appreciate your contributions.

If anyone wants to submit confidential experiences with polygraphs to legal pub, please email

Anonymous said...

Thanks for a nice discussion of this issue

drewpetersonexposed said...

Lie detectors. Blah!
Anything that has to do with this DA "Drew Peterson Exposed" book is pure marketing.
DA, JB, GS, and DP all trying to make a buck off a
murder of a woman. (or two)
All hype to try and sell a book.
Any person with average intelligence should be able to see right through it.
These guys have no morals, and make me sick to my stomach!
If you have been following this, Peterson was exposed a long time ago.
I think he killed Stacy and Kathleen. Maybe others too.
30+ years as a crooked cop.
(My opinion)

Anonymous said...

Ironically, Peterson supposedly passed the portion of the test about Savio's murder.

Lie detector tests are not reliable one way or the other!

Anonymous said...

Excellent coverage of lie detectors. Yes, ironic, Peterson supposedly passes the test as to Savio but fails as to Stacy. And there is no body for Stacy.

Anonymous said...

i know that my comment will be out of context but i love your blog
My question is ; where do i go to when a man tO WHOM i stayed married to for twenty five years in california;( we were poor and i was twenty five) has used his power to terrify me, lies all the time and had another life, took everything away from me through his power and i am destitute even though the courts gave me alimony and half of a fortune which he forced me to sign off under " the gun" yes i was scared and he told me " that i would never see my grandkids again" if i did not sign, where do i go now that i am seventy six and terrified?

Anonymous said...

Start with your state Legal Aide program. Tell them the story and see what they can do. Settlements procurred by fraud usually do not stand up if challenged. Also, if he threatened you physically, you may be able to have the prosecutor file charges.

Good luck.

Anonymous said...

Wonderful info on lie detectors!

Anonymous said...

Awesome explanation of lie detector tests.

Anonymous said...

Thanks for an understandable explanation.

California Surfer Dude said...

Are right folks, let Surfer Dude share with you his experience of a Lie Detector test.

I saved a geeky scientists life at the beach and he was so greatful that he gave me a Robot Lie Detector.

When I came home with the robot lie detector I decided to try it out on my son who came home from school two hours late.

When I asked where he had been he said he had been at the library.
The robot walked around the table and slapped my son knocking him to the ground.

Don't lie this robot has a built in lie detector. Now where were you?

Watching the 10 Commandments movie he said. Oncce again the robot knocked him to the floor.

Okay, it was a movie, but it was Dbbie Does Dallas he corrected himself.

I told my son that I was disappointed in him because I never lied to my parents. Just then the robot smacked me and almost knocked out my gold tooth.

My wife,at the time,chimed in, "Don't be too mad at him. After all, he is your son."

Just then the Robot Lie detector went over to my wife and hit her so hard that it knocked her out.

So that, your honor is why I will never submit to a lie detector test again...

Surfer Dude