The first, and most important, principle of true science is that the results obtained under conditions which are the same each time should be reproducable in order to be valid. Data that cannot be reproduced by different persons conducting the same test under the same conditions is considered to be invalid.
50 polygraph "operators" performing their shennanigans on the same test subject, using the exact same equipment, asking the exact same questions, in the exact same setting could not reproduce the same results as the first. The "charts" will vary every single time and the results will be interpreted incorrectly more than half the time. Some of the wrong interpretations will be reported as 'inconclusive' and the remainder will get the conclusion totally opposite from the facts.
I find the admission of Special Agent William Warner  of the FBI interrogation unit that polygraph is totally unreliable in its results quite fascinating and am curious why this article did not reach more people who could inform the masses, thereby debunking the myth that is polygraph and rendering it totally ineffective, at last putting this sham to rest.
I must, myself, submit to this sham again this month in my final probation-satisfying requirement. It will finally be the last I will ever have to endure. That comes as no solace when I am so strapped for financial resources that I will have no money with which to pay our electric bill this month and yet the court insists that I must throw money into the wind on this farce.
When queried as to the possible consequences of my failing this last polygraph, I was told that an immediate motion to revoke would then be issued from the probation department for failure to meet my probation conditions. They would do this because I did not "pass" a polygraph, though my court orders say, not that I must pass, but that I must answer all questions truthfully when taking the polygraph. They would have no corroborating testimony with which to back up the claim that I had lied on the test, no witnesses seeing me do something in violation of my terms, and yet the judge would very likely grant the motion to revoke.
Do not go to a court of law expecting justice. Go expecting the worst and be thankful if it does not come to pass.