Whether you believe polygraph examinations are rooted in the science of measuring human physiology or in "black magic" trickery perpetrated by sophisticated operators, there's no denying that polygraphs have come a long way over the past decade. Since the early '90s, polygraph technology has evolved from the old style ink-and-paper polygraph machines with their easily clogged pens to computerized solutions that can record, store, and analyze physiological data collected during a polygraph examination.

Polygraph exams are controversial. But controversial or not they are a useful law enforcement tool, and I'm never one to toss one of my best tools, especially one that can be as versatile as a polygraph.

The state of the art of contemporary polygraphs is the digital polygraph system, and one of the leading developers and manufacturers of this technology is Lafayette Instruments. Indiana-based Lafayette is the maker of the widely used LX-4000 computer polygraph system.

Consisting of Lafayette's LX 9.5 software, sensors, and a Windows platform portable or desktop computer, the LX-4000 computer polygraph system can do everything that the old pen-and-ink machines could do and much, much more. The LX-4000 can capture seven channels of data, including respiratory, cardio, and galvanic skin response readings.

The heart of the LX-4000 is the LX software, and the latest version, 9.5, is an excellent upgrade of what was already a powerful tool for polygraph examiners. Not only does this software facilitate polygraph examinations, its newest features include the ability to integrate audio and video tracks right into the chart. So besides getting the interpretation from your trained examiner, you'll be able to hear the subject's inflections and see his or her body language right on the computer screen.

To operate the latest version of the LX-4000 system and LX 9.5, you will need a computer that meets the following minimum requirements:

  • 1.0GHz Pentium III or higher with 256MB RAM and a 40GB hard drive
  • Windows 98/ME/2000/XP operating system
  • An available USB Port for the Data Acquisition System sensors
  • Digital sound card required for multimedia capabilities along with a digital video camera for video capture if desired and an external or built-in microphone for recording audio.

Security is one of the key concerns for anyone using a digital polygraph system. You have to be absolutely certain that the files cannot be hacked or altered. That's why the security features in LX 9.5 have been upgraded. Each operator's system can be secured by a user name and password. If you choose not to use the password protection, then security is monitored by the onboard auditing system, which tracks almost every nuance of the software's state and logs it. If someone else logs into your PC and tries to change or alter any important info, his or her access will either be denied or logged.

Another great feature of this software is that it gives the user the ability to choose his or her own setups. LX 9.5 is highly configurable, allowing the user to choose chart colors, printer types, video capture rates and methods, file naming conventions, and keyboard shortcuts.

All polygraphs collect physiological responses to questioning. The LX-4000 system accomplishes this using Lafayette Systems' Data Acquisition Systems (DAS) hardware interface. The sensors gather cardio, respiratory, and galvanic skin response data and import it via a single USB port into the software where it is digitally recorded and displayed in real time.[PAGEBREAK]

LX 9.5 also facilitates the process of creating a subject's biographical record and pre-examination record. A standard set of questions that can be used to capture personal history data on each tested subject is pre-programmed into the software and displays in a dialog box. I'd prefer to see an entire window opened, so that the user could see all the questions rather than scrolling down through a list, but this feature is very useful. And if you don't like the preformatted questions, you can use your own. The designers left room to create 10 more Yes/No-type questions appropriate for your department or your specific case.

Other subject prep features include a database that allows you to check if any prescription or over-the-counter medications and even any illegal drugs that the subject admits to taking will affect the test. In addition, biometric fields such as fingerprints and photos can be captured and made part of the permanent record for positive identification for any followup questioning by investigators.

LX 9.5 also comes with several questions templates. A template is a question set that may be used as the basis for creating other question sets or as a question set containing commonly asked questions. New questions are easily created with a drag-and-drop interface, and they can be color coded for relevance or "control" irrelevant questions.

Once you have the questions prepared, editing, if necessary, is a simple point-and-click or cut-and-paste operation. This is a real time-saver if new facts are discovered during the pre-test interview. Since no answer in an examination should be a surprise, if one comes up during the preparation, you won't have to go back and change it in multiple places.

After you've completed the tests, the scoring begins. LX 9.5 not only allows scoring using the Objective Scoring System (OSS) applied by the polygraph operator, it also lets you run algorithms such as POLYSCORE developed by Johns Hopkins University, or Quest, the Quantitative Evaluation System that graphically displays relative reaction strengths with color-coded bar graph or hodograph. Also available is IDENTIFI, which utilizes a three- or seven-position scale, allows an examiner to analyze relevant questions against weaker adjacent or preceding comparison questions. This algorithm will score many different examination types, including screening tests such as preemployment and security examinations. If that's not enough, and sometimes its not, LX 9.5 provides a built-in e-mail function that packages up all the necessary files, lets you password protect them if you choose, and zips them off to a colleague across the Internet for his or her interpretation.

When you've reached a consensus, LX-4000 even helps you document your analysis. The software interfaces with three standard word processors so you can draw on its data while writing your report.

It's been said that confession is good for the soul. Well, when you combine a well- trained and experienced polygraph operator and Lafayette Instruments' LX 9.5, you might just see the number of confessions rising in the near future.

A 25-year police veteran, Bob Davis currently runs the San Diego Police Department's computer lab.

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