[Rejecting P1] The jury would still be in charge of determining guilt.
[Rejecting P2] The polygraph test results would just be another piece of evidence. It would not form the basis of a guilty verdict, but nor would it be dismissed.
[Rejecting P3] Lie detectors are a useful tool for establishing deceit.
Therefore, they should be used, alongside other legal tools to measure deceit, and be admissible in the court of law.