Ps sued Cryobank (D) for professional negligence, fraud, and breach of contract. Ds sold Ps frozen sperm specimens donated by Donor No. 276. Ps signed D's form agreement that provided, in relevant part, that 'Cryobank shall destroy all information and records which they may have as to the identity of said donor, it being the intention of all parties that the identity of said donor shall be and forever remain anonymous.' D assured Ps that the anonymous sperm donor had been fully tested and genetically screened. Brittany was born on April 18, 1989. In May 1995, Ps were informed that Brittany was positively diagnosed with ADPKD. It was Donor No. 276 who genetically transmitted ADPKD to Brittany. D learned that the donor's mother and his mother's sister both suffered from kidney disease and hypertension, and the donor's mother suffered a 30 percent hearing loss before the age of 60. The presence of multiple instances of kidney disease coupled with hypertension and neurological disorders, such as deafness, are red flag indicators of the presence of ADPKD in Donor No. 276's family, and thus, Ds knew that Donor No. 276's sperm could be at risk of genetically transferring kidney disease. Ps allege that D falsely represented to Ps that the sperm they were purchasing was tested and screened for infectious and genetically transferable diseases and safe to effectuate their pregnancy. Ps propounded discovery to D seeking information regarding Donor No. 276, including his name, address, and medical history. D objected to providing any information regarding Donor No. 276, claiming the donor's right to privacy and his physician-patient privilege. Donor No. 276 had sold 320 deposits of his semen to D and had received a total of $11,200 for his sperm. Ps argued that they were entitled to have all of Donor No. 276's medical information in D's possession and disclosure of Donor No. 276's identity so that they could question him directly because the information (1) was relevant to the issues in the litigation, and (2) was necessary 'as a predictor of the medical fate of Brittany' and is 'one of the most reliable indicators of Brittany's future.' The trial court granted Ps' motions and D filed a petition for writ of mandate. It was denied, and Ds then petitioned the Supreme Court for review. The Supreme Court granted review and transferred the matter with directions to vacate the order denying mandate and issue an order directing the trial court to show cause why relief should not be granted. The appeals court issued an alternative writ of mandate. The trial court responded in August 1997 by vacating its order granting Ds' motion. Ps then located real party John Doe, who they believe is Donor No. 276. Ps served him with deposition and trial subpoenas in September 1998. Eventually, Ps moved to compel that John Doe comply with the subpoena to attend his deposition and produce the requested documents. On November 2, 1999, the trial court denied Ps'' motion. This petition followed.