Can a lab tech detect old urine?

For the last two years SOME labs have been testing for synthetic urine. When you get caught, they usually have you come in the next day to retest. So it depends on the lab. If it is just a simple 5 panel test that they dip the stick into on the spot, you won't get caught, but if they send it out to a lab, there is a chance they will discover that it is synthetic.