It doesn't matter who the "expert" is, the prosecution, defence or accuser will always find someone to support their argument either way, but that this does not mean that the expert is not an expert in his field. In this case, this particular expert is clearly that, with many years flying and engineering experience, ATPL, reg35, instructor rating etc etc. Remember that the 5 degrees is a comment of the reporter and may not reflect those words testified by the expert. The ONLY way to confirm this prior to pointing the finger and dismissing his opinion would be via the court transcripts.