If the markings of a field are incorrect, in this case, specifically the penalty mark, should the existing mark be used, or should the referee mark off the correct distance? This is on an artificial field, so it cannot be covered or moved easily.
USSF answer (August 5, 2008):
If the penalty mark is in the wrong place and cannot, for whatever reason, be changed, the referee must ensure that any penalty kicks are taken from the correct distance from the goal line and in the correct location in relation to both goal posts. Possible mismarked lines can be worked with, but the penalty kick occurs so rarely and can be so decisive, that the distance MUST be correct.