Polygraphs are an incredibly popular tool. They are used in criminal and civil cases, by the prosecution and defense alike, to determine the credibility of sources, defendants, and suspects. However, polygraphs are incredibly problematic. As has been shown by various scientific reports and assessments, they have zero scientific basis, are far too open to individual bias and partial interpretation, and incredibly unreliable. Yet they are in use by nearly every federal law enforcement agency for employment and investigative purposes and are utilized by the courts in certain circumstances. My own view on polygraphs is rather negative, having personally researched the issue and been the subject of such an exam for employment purposes.
Targeted killing operations only make sense if they are used as a deterrent or if a certain target is important enough that his/her death would deal a significant blow to the adversary nation state. To be a target of interest, you have to be irreplaceable. If someone can take your place half an hour after your death and continue your work, assassination is meaningless.