If you are conducting a review for privileged documents and looking for an authoritative guide, consult A Practitioner's Summary Guide To The Attorney-Client Privilege And The Work Product Doctrine, posted by McGuire Woods LLP. In addition to looking for attorney-client communications, and checking to see if there are documents which constitute work product, keep in mind the following key points about privilege review:
Fiduciary Exception - a beneficiary cannot be denied access to communications between a lawyer and a trustee about the administration of a trust.
Garner Doctrine - the shareholders of a corporation may have access to attorney-client communications, because they are the true clients. Not all courts accept the Garner Doctrine.
Settlor Exception - the fiduciary exception does not apply to the creation or termination of ERISA plans.
Unprotected Background Information - logistical details of an attorney-client relationship are not protected. So for example, the date a client was referred to an attorney, or the length of an attorney's representation of a client would not be protected.
Crime-Fraud Exception - communications about a client's criminal, fraudulent, or egregiously improper conduct are not protected. This applies to future acts, not acts which have already be taken.
Joint Defense / Common Interest Doctrine - co-defendants can share privileged communications without waiving the protection. The represented parties will usually have to anticipate litigation in order for the communications to be protected.
Implied Waiver - privilege can be waived if the holder of the privilege relies on the communications.
Overcoming Work Product Protection - the protection may not apply in subsequent, unrelated litigation. A criminal defendant who is exonerated can request work product in a later civil case.
Federal Rule of Evidence 612 - documents used to refresh a witness's recollection must be disclosed.
Subject Matter Waiver - is more common for attorney-client communications than for work product. Disclosing a non-testifying expert's report and producing work product in discovery to a third party does not result in subject matter waiver, but using work product in testimony or letting an employee keep work product after they are terminated will result in subject matter waiver.
Hearn Doctrine - at issue waiver can take place if a party asserts knowledge or ignorance of an important fact. So if the privileged communications will determine the outcome of a case, and there is no other source for the relevant information, then privilege can be waived.