The Attorney-Client Privilege is one of the key doctrines of our legal system, but there are exceptions as explained by the Wills, Trusts & Estates Prof Blog in "Treasure-Hunter's Documents Might Be in Deep Water."
This doctrine even has an important place in Estate Planning because in order to create an estate plan the client needs to be able to tell the estate planning attorney about their assets. But the client might not be willing to reveal everything if the attorney could later be forced to testify in a legal dispute.
In the case discussed, a former treasure hunter hired an attorney to create an offshore trust. The client then got financing for an expedition in which he recovered gold from a sunken ship. However, the client then refused to pay the people who had financed his treasure hunt, and they are asking the Court to force the attorney to reveal the trust documents so that they will have an easier time recovering the money.
The Judge in the case, while not making a decision, has acknowledged that the crime-fraud exception to attorney-client privilege might apply in this case. In other words, if an attorney's services are knowingly used to commit a crime or a fraud, then the Attorney-Client Privilege does not apply.
A qualified Estate Planning attorney can guide you in creating an estate plan that meets your unique needs, and explain the exceptions to the Attorney-Client Privilege that could be applicable in the context of estate planning.
Reference: Wills, Trusts & Estates Prof Blog (Nov. 17, 2016) "Treasure-Hunter's Documents Might Be in Deep Water."