Not sure you are using "capacity" correctly, but I assume you are asking what my qualifications are as an expert.

My job in this case was to review the available information (which I outlined above) about the case and render an opinion on the facts in evidence relative to the safe operation of model aircraft.

My opinion was based on:

40 years of active modeling across a large variety of interests (power, giant scale, gliders, electric, etc.)
Successfully and safely running 27 large giant scale aerobatic contests (40 to 50 pilots)
Participation in a very large number of organized model airplane events and contests
Current Chairman of the IMAC Rules and Standards Committee (which includes helping to develop the guidelines for safe operation of contests)
Exposure to a large number and variety of flying sites due to extensive travel around the US and participation in a wide array of events at a large number of locations
Thorough knowledge of the AMA Safety Code and other guidelines of the AMA that impact safety.
Knowledge of the accident site and familiarity with normal operations at that site
Extensive knowledge of a wide variety of aircraft and past experiences with distractions and responses while flying radio control models.

Those are the highlights. The judge was satisfied and the plaintiff was unsuccessful in his challenge of my qualifications.

Oh, and I clean up real good and own a suit and tie.