Petitioner was sentenced to 13 years in state prison in 1991. He was first committed to the State Department of Mental Health as mentally disordered offender (MDO) in 2000, and that commitment was extended annually from 2001 to 2004. Thirteen days after his last term expired, a petition for recommitment was filed. The prosecutor conceded that there was no good cause for the late filing of the petition to extend the commitment. Petitioner’s motion to dismiss the petition was denied, and he sought a writ of prohibition and mandate, alleging that there was no legal basis for his detention. The appellate court granted a writ of mandate directing the superior court to vacate its order denying petitioner’s motion to dismiss and overruling his demurrer. The overwhelming weight of authority suggests that the unexcused late filing of an MDO recommitment petition means the prisoner can no longer be involuntarily held as an MDO. To hold otherwise would mean that no timely governmental action would be required to hold MDO’s indefinitely beyond the expiration of their legal commitment period.