How did it get this far in the process for a judge to say that there was a lack of evidence of disorderly conduct?

According to this story, the Boston Police Department used High-Definition TV to determine that Chris House was doing everything BUT reaching for the ball when he made contact with Sheffield last month while at Fenway.

Granted, I don't think what House did was malicious. He appeared to be just another drunk fan reaching for the ball in play. But for the police department to rule that it was disorderly conduct, they had to have had something to go on. I guess the real question is, what is "probable cause?" To me the definition would be,reaching into the area of play and interferring with the player or ball.