Puh-leeze! You're exagerrating.
These three young men did something really, really stupid and they ended up with a lot of negative attention. More than likely their relatives all jumped down their throats and now to save face the three are spouting lies.
Taking a polygraph for something like this is not a life or death event, it is a "no brainer". The fact they've refused, and Eunice Stone has not speaks volumns about her integrity.
Coming clean and telling the truth would be mature. Frankly, I wouldn't want any of the three as my doctor, since they neither tell the truth nor take responsibility for their actions.
Do you draw the same conclusion about Anita Hill, who took a polygraph, and Clarence Thomas, who wouldn't?