What is the reasonableness defense?

The introduction of this new legal theory, the 'reasonableness' defense, after almost a year of discovery, illustrates, quite clearly, the difficulties inherent in any attempt to confine the relevancy standards to a rigid formula: frequently, as in the instant case, the nature of the facts that will be relevant and admissible at trial cannot accurately be determined at the pretrial stage of application for discovery. Thus, for example, we now know that the subject matter of the action may include not only the facts concerning the actual monitoring of the phone line and possible eavesdropping and communications with the police, as initially suggested by the allegations of the complaint, but also may encompass the information relied on by the defendants before their decision to monitor, including the reasonableness of the scope and intensity of the intrusion into plaintiff's privacy. We could not properly rule at this time on either the validity of this asserted affirmative defense, or on the evidence which may be relevant to it, if proper; in any case, whether the defense is a valid one or not, the parties are entitled to undertake discovery with reference to the matters potentially involved. (See Chapin v. Superior Court, supra, 239 Cal.App.2d 851, 858--859, 49 Cal.Rptr. 199.)