How do you measure it it has been effective when the successful liar passes the test and is not defined as such?

If you catch X people trying to blow up a plane and no planes get blown up, that's fairly good evidence that your method of catching people trying to blow up planes has been 100% successful. So far.

This is one hell of a post hoc ergo propter hoc, I'll give you that at least

What's wrong with it? He's not making the usual "tiger-proof rock" argument used to refer to the TSA, after all. The TSA doesn't, as a rule, catch people who were actually planning to cause trouble. They either catch people who didn't know/care how much toothpaste they were allowed to smuggle onboard, or they catch idiots who forgot they were carrying a .50 caliber Desert Eagle in their shaving kit. This is a different argument altogether.

That is an extraordinarily dangerous notion.

Or maybe the people trying to blow up planes are just as bad at blowing up planes as you are at catching them.

Want to buy an elephant whistle?

The difference is that there are many groups who have publicly declared their intent to blow up Israeli airliners, so it's not as if you're defending against a non-existent threat.

No, but if my security guards keep turning away actual elephants at the border and I find no actual elephants nearby then I can conclude that my anti-elephant security works.

Do you know that you have a banana in your ear?

You raise an interesting conundrum, but you can tell of a certain success rate by the number of liars who eventually confess to lying or are found to have been lying.

Wouldn't that be just the same case as with the caught liars but extended to a group of people who despite being successful at the interview failed fulfilling the task? There is still an unknown group of "liars" who passed the test and never confessed.

They could be lying about whether they were lying in the past.

We're talking about legal contexts here. Almost no one, unless coerced/brutalized by police/DAs, admits to crimes they did not commit. And the you have the thing where you can verify their admission of guilt with corroborating details.

There have many many many cases of individuals getting behind bars because they have been coerced to plead guilty and confess to crimes that they never committed.

"unless coerced/brutalized by police/DAs" is not really exceptional, once in a decade, type case, sadly it is rather routine.

I know personally a person who plea-bargained, which means admitting to a crime they didn't commit, because the likelihood of being convicted (and the penalty of conviction) was so great a threat. He pled to a lesser crime (that he also didn't commit) and served 5 years.

Sadly, there is a systematic problem in which many must plead guilty because they will be punished beyond measure if they do not. It is structural and endemic in American justice:

http://www.nybooks.com/articles/archives/2014/nov/20/why-inn...

(EDIT: And this one) http://www.nytimes.com/2015/08/16/magazine/the-bail-trap.htm...

General level of terror in Israel? It is absurdly low compared to the threats that surround them (lets not go into if such threats are warranted or not)