Everyone below has offered good explanations, but I'd like to make one further point. Typically, people take the fifth when they are on trial. The lawyers were

Everyone below has offered good explanations, but I'd like to make one further point. Typically, people take the fifth when they are on trial. The lawyers were not on trial; they were there as part of the court, and were supposed to not be involved in the matter. By taking the fifth, they are admitting "I am involved in the matter."