Considering that part of the cost of every litre of diesel is a tax levy called the illuminating paraffin (IP) tracer dye levy whose purpose is to curtail the unlawful mixing of diesel and IP and following the recent scandal of 70 petrol stations across the Republic reported to have mixed their diesel with paraffin, how did the dye tracing mechanism borne out of the levy fail to detect the contaminated diesel before it got sold to consumers?