How Many Shots? Varying Opinions
First of all, these are not all "opinions". If they are relating what they recall hearing, they are giving evidence. If they do not recall the number of shots but, in analysing it later, figure that they heard a certain number of shots, they are giving an opinion rather than a recollection of events. It is important to separate opinion from memory recall and that can only be done through careful questioning which, in most cases, did not take place. The best way to separate recollection from opinion is to look at the earliest statements of witnesses and see what they recalled voluntarily.
With a large number of witnesses, the witnesses are seldom in complete agreement on even the most salient details (ie. details that more than 50% of witnesses to an event recall voluntarily). So it is hardly surprising that some witnesses disagree with others. With at least 132 witnesses, it would be more surprising if all witnesses agreed. Studies have shown that witnesses are generally 90%-95% accurate in recalling salient details: See:
Loftus, Eyewitness Testimony (1979) p. 25-31One has to look at all the evidence and determine whether any conclusion can be drawn with any level of confidence. In looking at all the evidence, it is not difficult to conclude with a high level of confidence that there were exactly three loud sounds heard.