Lawyers fairly often receive the other side’s privileged, confidential, or stolen information. The other side might inadvertently send an otherwise privileged email to the lawyer or include privileged documents in disclosure materials; the other side’s disgruntled former paralegal might—in an obviously unauthorized act—deliver a privileged document to the lawyer; or the client’s former coworker (and mole) might steal documents for the client and turn them over to the lawyer. Another frequently occurring situation is when a prospective client (see Model Rule 1.18) discloses confidential information to the lawyer in an initial consultation, no attorney-client relationship results, and the lawyer or the lawyer’s firm later represents an adverse party. When these problems come to light, the other side might well move for the lawyer’s disqualification—either because the lawyer used unethical means to obtain the information or because the lawyer’s exposure to the information raises fairness concerns.
 Consequently, court rules and many ethics opinions and commentators have generally addressed the inadvertent or unauthorized receipt of such information. See, e.g., Fed. R. Civ. P. 26(b)(5)(B); Model Rules R. 4.4(b); Ariz. Comm. on the Rules of Prof’l Conduct, Formal Op. 01-04 (2001); Andrew M. Perlman, The Legal Ethics of Metadata Mining, 43 Akron L. Rev. 785 (2010); [click here for an ABA list of state metadata ethics opinions.]
 See, e.g., Cnty. of Los Angeles v. Superior Ct., 222 Cal. App. 3d 647, 657-58, 271 Cal. Rptr. 698, 705 (Ct. App. 1990) (“We hold that a party may, for tactical reasons, withdraw a previously designated expert witness, not yet deposed. If that expert continues his or her relationship with the party as a consultant, the opposing party is barred from communicating with the expert and from retaining him or her as the opposing party’s expert. . . . When an attorney violates this rule, he or she must be recused. Having become privy to an opposing attorney’s work product, there is no way the offending attorney could separate that knowledge from his or her preparation of the case.”); MMR/Wallace Power & Indus., Inc. v. Thames Assocs., 764 F. Supp. 712, 726-27 (D. Conn. 1991) (granting disqualification in part because attorney presumably obtained confidential information from the moving party’s former employee); In re Beiny, 132 A.D.2d 190, 195–96, 522 N.Y.S.2d 511 (N.Y. App. Div. 1987) (affirming disqualification because the firm’s receipt, review, and use of privileged information involved “intentional misconduct” and was otherwise warranted by “the resulting prejudice to the trustee against whom the improperly obtained materials were used extensively both individually and en masse, the need to assure the trustee that the wrongfully acquired information would not be used prospectively, the need to sanction adequately the blatant misconduct involved so as to deprive the offending attorney and law firm of any benefit possibly to be deprived therefrom, and the need to deter similar abuses which seriously compromise the integrity of the judicial process”); Merits Incentives, LLC v. Eighth Jud. Dist. Ct., 262 P.3d 720, 725–26 (Nev. 2011) (denying disqualification because attorney promptly notified opposing counsel after receiving its documents on disk from an anonymous source); In re Meador, 968 S.W.2d 346, 351-52 (Tex. 1998) (denying disqualification, noting that “it is impossible to articulate a bright-line standard for disqualification where a lawyer, through no wrongdoing of his or her own, receives an opponent’s privileged materials,” and noting that in “this exercise of judicial discretion, a trial court should consider, among others, these factors: 1) whether the attorney knew or should have known that the material was privileged; 2) the promptness with which the attorney notifies the opposing side that he or she has received its privileged information; 3) the extent to which the attorney reviews and digests the privileged information; 4) the significance of the privileged information; i.e., the extent to which its disclosure may prejudice the movant’s claim or defense, and the extent to which return of the documents will mitigate that prejudice; 5) the extent to which movant may be at fault for the unauthorized disclosure; 6) the extent to which the nonmovant will suffer prejudice from the disqualification of his or her attorney”).
[Source: Keith Swisher, The Practice and Theory of Lawyer Disqualification, 27 Geo. J. Legal Ethics 71 (2014)]