May a lawyer represent a new client whose case attacks a former client serving as an adverse witness?

Plain-English summary

Client B sought representation in a case alleging wrongdoing by former client A, who would be an adverse witness but not a named defendant.

The opinion permits representation unless the lawyer acquired information during the prior representation that could harm A in B’s case. It says B should be told about the earlier representation, without revealing information beyond that fact or matters generally known.

Currency note

This opinion was issued in 1996, before Missouri’s 2007 revisions to the Rules of Professional Conduct. Subsequent rule amendments or later opinions may have changed the analysis. Treat this page as historical context and verify current rules before relying on it.

Common questions

Q: Does A’s status as an adverse witness automatically bar the case?

A: No. The answer makes the result depend on whether the lawyer acquired information usable against A.

Q: What may be disclosed to B about the old matter?

A: The fact of the former representation and information that has become generally known, but no more.

Background and rules framework

The answer applies Rule 4-1.9(b) to confidential information from the earlier representation.

Citations and references

Missouri Rules of Professional Conduct:

• Rule 4-1.9(b)

See also

• Missouri Informal Op. 960263: Company Witness Impeachment
• Missouri Informal Op. 970092: Former Municipal Client

Source

• Landing page: https://mo-legal-ethics.org/informal-opinion/960248/
• Rule revision reference: Missouri Informal Opinion 970082

Original opinion text

Reproduced from the official source for research purposes. The linked source is authoritative.

QUESTION: Attorney has been approached by Client B for representation. In the case, Client B will make allegations against Client A who is a former client of Attorney. Client A will not actually be a named defendant but will be an adverse witness. ANSWER: Under Rule 4–1.9(b), Attorney may represent Client B unless Attorney obtained information in the course of representing Client A that could be used to the detriment of Client A in the course of representing Client B. Attorney should disclose Attorney´s previous representation of Client A to Client B, without disclosing any information beyond the fact of the representation and information which has become generally known.