THE MUMBAI police, which has been unable to track down Arshad Khan, a key witness in the Ghatkopar hoarding collapse case, is in the process of approaching the court seeking to issue a notice to Khan to appear before the police, failing which he could be declared as an absconder. The SIT probing the case in which 17 people had died had summoned Khan to record his statement, but he did not turn up. Khan was not found at his residence and his phone was switched off too. Police have…