How is a party in interest defined? I have a prospect, the company has an investment committee to decide what to trade. The owner of the company and his son are members of the investment committee. The plan is invested in a mutual fund where another son of the owner is the "fund manager" --- does this make the son that is the "fund manager" a party in interest?

Party-in-Interest is defined in ERISA 3(14). ERISA 406 prohibits a fiduciary from engaging the plan in certain transactions with a party-in-interest. You also have the IRC 4975 definition of a disqualified person.

This is a very complex area of the law, in which I am not expert. Some of the other folks on this board are, and may be able to give you answers to some specific questions - but it isn't an area to take chances with. See ERISA counsel locally.

11-4 edit on the above IRC section reference - I just noticed that my magic thumbs had transposed a couple of numbers.