Then read the LBTLD, as you have no recourse but to take the it or change career paths.
Main point, polygraph is nothing more than an interrogation (fishing expedition for employment polygraphs). They try to CONVINCE you the machine can actually detect deception on your part. THEN, falsely claim that one or more of the test questions indicates YOU ARE LYING, or holding back. All a ploy to see what they can get you to say.
So, if you go in KNOWING (without any doubt) the machine CAN NOT detect lies, and they are just trying to bluff you and see what they can "get you to say", then you will be one step ahead of most other applicants. Most people believe in the myth of the polygraph, and fall for their little game. So when told by the examiner they are "showing deception" on this or that question, THEY ACTUALLY BELIEVE IT, and start yacking like an old church lady. It is amazing what they can get people to admit to.
Of course, you don't want the examiner to know you are savvy tot all this. You can't beat a "con" game, if the conman knows you are aware of the "con". So on one level, it's letting the examiner think he/she has "flustered" you, but not giving up anything that would "raise an eyebrow". And all it has to do is "raise an eyebrow". Doesn't have to be a crime...etc. One should ask themselves "Would I want the hiring authority to hear this?" Don't admit to anything you haven't already disclosed on the security application!! And the info requested on your application is quite specific and above certain thresholds. Have you taken drugs in the past XXX months? Have you committed any major crimes? Not very ambiguous, is it?
Of course, there is still the squiggly marks on the chart that must meet their established parameters. Most people focus most of their worry and attention on what the machine is saying, and trying to make it say "something else". They totally stop paying attention to the stupid dumb ass shit they are admitting to the examiner! Again, usually because they actually believe the machine, NOT THEMSELVES!
Of course, if you take drugs, have committed crimes in the recent past, download kiddie porn, lied like a politician on your application, spend your time off in airport restroom stalls tapping your feet...etc., you should admit to it. But then why would you apply to a LE job?
Good Luck
TC