Robert,

A "single issue" (sometimes also called "specific issue") polygraph examination is one concerning a single matter, for example, a bank robbery. Generally, some form of "Zone Comparison Test" (ZCT) is used for this purpose. A "multiple issue" polygraph examination would involve two or more matters, for example, a bank robbery and a liquor store robbery. Some variety of "Modified General Question Test" (MGQT) is generally used for this purpose.

A "specific incident"  polygraph examination (also sometimes referred to as a "specific issue" examination, creating confusion) is one concerning an incident known to have occurred, such as, again, a bank robbery. Specific incident polygraph examinations stand in contrast to screening examinations, in which the relevant questions are about matters not known to have occurred.

CQT polygraphy, whether used for specific incident or screening purposes, has no validity as a diagnostic technique: it has absolutely no grounding in the scientific method.

However, in specific incident examinations (regarding crimes known to have occurred), the polygraph examiner will often have supplemental information apart from the polygraph charts that may help him/her to make a determination of truth versus deception (e.g., the fact that a certain subject had the means and motive to commit the crime, and has no alibi). In such cases the polygraph examiner might well arrive at correct decisions more than half the time, but this does not confer scientific validity on CQT polygraphy. As the National Academy of Sciences noted in its polygraph report, there is essentially no evidence on the additive validity of polygraph, that is, its ability to add diagnostic value to that which can be achieved without the polygraph (e.g., interrogating a suspect without the use of a polygraph, or with a mock-up device that the subject is led to believe is a polygraph).

Robert,

You're very welcome. If you know others who may someday face a polygraph interrogation, I hope you'll pass on to them what you've learned.