Polygraphs are unreliable and subject to manipulation. You can do that by asking the right questions, or with certain tradecraft-style techniques to defeat the device.
Who initiated this polygraph? The alleged offender's counsel? If so, it's useless, nobody would ever polygraph their client without coaching, without knowing the answers to the questions being asked, or without vetting the questions.
A polygraph conducted by law enforcement or a court might be of slight interest. But one arranged by one party's counsel, without any risk on "non-sympathetic" questions? Publicity stunt.