TRENTON -- A leaking roof shut down a courtroom in the century-old Mercer County criminal courthouse yesterday. The courtroom where Superior Court Judge Darlene Pereksta presides -- the same courtroom where part of the ceiling collapsed in 2003, narrowly missing a defense lawyer -- was closed yesterday due to the collapse of more ceiling tiles, officials said. Water, probably pushed into cracks in the roof by the recent high winds, soaked the plaster and caused it to crumble and fall. The falling plaster knocked down about six ceiling tiles underneath it, said Pete Daly, a spokesman for Mercer County. The leaks were fixed yesterday with a temporary sealant but the courtroom remained closed while air quality tests were performed, Daly said.