var grIncident = new GlideRecord('incident');
grIncident.addExtraField("caller_id.department.dept_head.name"); 
grIncident.addQuery("sys_id", "c74706c61b670094bd8120a13d4bcb03");
grIncident.query();
 
while(grIncident.next()){
  gs.info(grIncident.caller_id.department.dept_head.name.getDisplayValue())
}