Polygraph tests are are not real science, it's not supported by hard evidence.
"Polygraphs measure arousal, which can be affected by anxiety, anxiety disorders such as posttraumatic stress disorder (PTSD), nervousness, fear, confusion, hypoglycemia, psychosis, depression, substance induced states (nicotine, stimulants), substance withdrawal state (alcohol withdrawal) or other emotions; polygraphs do not measure "lies". A polygraph cannot differentiate anxiety caused by dishonesty and anxiety caused by something else."
A poly will measure anxiety, which would you believe it could be caused by the act of simply being accused of a crime. If a random person got accused of being a pedophile would it be an indication of guilt that they find the situation stressful & anxiety inducing?.