The 'trained observers' are knowledgeable and passionate baseball people, not random Joes off the street. Many of them are former players, managers, scouts, etc. They have to pass a difficult test, which includes things like charting pitches, before they will even be considered to be a video scout. Then they go through intense training and practice. I imagine that anyone whose scoring is out of line with the others would be eliminated. Also, the 'trained observers' are rotated regularly to avoid bias.