Test for whether discovery/documents about a 3rd party breaches privacy rights

Documents implicate privacy rights when the documents include any information that is not public, such as unlisted phone numbers, financial information, health information, or anything else the person would not want others to see or know--including whether a person has failed to pay certain bills including rent. I think you are asking about the test for determining if the documents, even though private, are discoverable. Courts in California use a balancing test. In other words, the judge is required to balance the nature and extent of the private right invaded with the necessity the litigant has for the discovery. If the discovery is only slightly important, then privacy rights will trump discovery, and the litigant will not get the documents. If the discovery bears directly on a critical issue, discovery may trump privacy, although the court will probably make orders designed to protect the privacy of any third person (such as requiring redacting or disallowing any further dissemination of the documents). Courts are more likely to determine that privacy trumps discovery if the litigants are seeking discovery from or about people who are not parties to the litigation. In an unlawful detainer action, a defendant who has not paid rent is not likely to be able to obtain private information about other tenants because it is not likely that what has happened to other tenants bears directly on the defendant's defenses. If you believe you have a legitimate defense of some sort of discrimination or habitability claim that could be furthered by discovery from your co-tenants, you should seek a lawyer's assistance. This is not the kind of case you should try to litigate yourself.

This is an extremely broad question, but hopefully this explanation helps. California courts have generally concluded that the public interest in preserving confidential information outweighs the interest of a private litigant in obtaining the confidential information. (San Diego Trolley, Inc. v. Superior Court (2001) 87 Cal.App.4th 1083, 1098 , citing Harding Lawson Associates v. Superior Court (1992) 10 Cal.App.4th 7, 10.) For example, in employment cases, "The balance will favor privacy for confidential information in third party personnel files unless the litigant can show a compelling need for the particular documents and that the information cannot reasonably be obtained through depositions or from nonconfidential sources. [Citation.] Even when the balance does weigh in favor of disclosure, the scope of disclosure must be narrowly circumscribed. [Citation.]" (Harding Lawson Associates v. Superior Court (1992) 10 Cal. App. 4th at p. 10.) In California, the constitutional right to privacy extends to one's personal financial information. Valley Bank of Nevada v. Superior Court (1975) 15 Cal.3d 652, 656 (“we may safely assume that the right of privacy extends to one's confidential financial affairs as well as to the details of one's personal life”). Tax returns are also privileged. Deary v. Superior Court (2001) 87 Cal.App.4th 1072, 1078 (including those of corporations and estates). As are W-2s. Brown v. Superior Court (1977) 71 Cal.App.3d 141, 143. This “does not mean that parties who come to court, voluntarily or not, are entitled to privacy in respect of court records that are . . . presumptively public records.” Burkle v. Burkle (2006) 135 Cal.App.4th 1045, 1063-64. Rather, only “if there is a substantial probability of prejudice to a privacy interest of higher value than the public's right of access to court records” (such as avoidance of identity theft or other crimes relating to the misuse of personal financial information), is a sealing order proper — as long as it is narrowly tailored to serve that overriding interest, and there is no less restrictive means of achieving the overriding interest. Id. at 1063-67; see CRC, rule 2.550(d); see also NBC Subsidiary (KNBC-TV), Inc. v. Superior Court (1999) 20 Cal.4th 1178, 1222. Article 1, section 3 of the California Constitution, which guarantees the right of access, provides expressly that nothing there “supersedes or modifies the right of privacy guaranteed by Section 1 or affects the construction of any statute, court rule, or other authority to the extent that it protects that right to privacy.”Cal. Const. Art. 1, § 3(b)(3); see Sacramento County Employees' Retirement System v. Superior Court (2011) 195 Cal.App.4th 440, 454. In order to justify encroachment on the right to privacy, the party seeking records must demonstrate a “compelling need for the particular documents.” Ombudsman Services of Northern California v. Superior Court (2007) 154 Cal.App.4th 1233, 1252. Finally, note that C.C.P. §1985.3 requires a party subpoenaing certain types of records such as bank records from a consumer to attach a notice of the consumer’s rights to the subpoena and serve such notice on the consumer. A party seeking private records must demonstrate a compelling need for the requested information, which balances against the privacy interests at issue, and must also demonstrate compliance with C.C.P. §1985.3.