Assistant prosecutors in Jackson County have voted to join a union. More than 90% of about 70 assistants who work in Kansas City have voted to join Local 42 of the International Association of Fire Fighters. A spokesman for the group says it chose the firefighters’ union because it has the political clout to get its members more pay. Assistants in the Jackson County prosecutor’s office start at $32,000 dollars. Some take second jobs to earn more money.