Where functions of the pretrial services agency have been delegated to a probation department or other arm of the court under Section 3, their records shall be segregated from other records. Two years after the date of the first interview with a pretrial services agency representative, the defendant may apply to the chief circuit judge, or a judge designated by the chief circuit judge for these purposes, for an order expunging from the records of the pretrial services agency all files pertaining to the defendant.