A day after the father of a 16-year- old suspect in the Gurgaon schoolboy killing filed a plea against his son's CBI custody, the vicitm's father today said the petition would be challenged in the court. The father of the suspect had yesterday filed the plea against three-day custody of his son given to the Central Bureau of Investigation by the Juvenile Justice Board. The petition said the board "erroneously and illegally" granted remand to the CBI and demanded that every other action taken by the agency pursuant to the legal order be established null and void.