What must a lawyer check before taking an unrelated case against a former litigation client?

Plain-English summary

A lawyer had concluded litigation for Client A and was asked by a new client to act against Client A.

Assuming the two cases were not substantially related, the opinion identified a possible conflict under Rule 4-1.9(b). It said the lawyer had to determine whether information acquired while representing Client A could be used to Client A's detriment in the current action. It did not make a final conflict determination without that fact.

Currency note

This 1995 opinion predates Missouri's 2007 amendments to its Rules of Professional Conduct. An official reference note identifies July 1, 2007 amendments to Rules 4-1.9 and 4-1.10. 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: Did unrelated subject matter automatically permit the new representation?

A: No. The opinion identified a possible Rule 4-1.9(b) conflict even on that assumption.

Q: What fact controlled the opinion's further analysis?

A: Whether the lawyer had acquired information in the earlier representation that could be used to the former client's detriment.

Background and rules framework

The opinion applied Missouri Rule 4-1.9(b) to a new adverse representation following concluded litigation, expressly assuming the matters were not substantially related.

Citations and references

Rules of Professional Conduct:

• Missouri Rule 4-1.9(b)

See also

• Missouri Informal Op. 950123: Firm's former spouse client
• Missouri Informal Op. 950174: Former firm prenup conflict

Source

• Landing page: https://mo-legal-ethics.org/informal-opinion/950116/

Original opinion text

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

QUESTION: Attorney represented Client A in litigation which has concluded. Attorney has a new client who would like Attorney to provide representation against Client A. Does Attorney have a conflict? ANSWER: Assuming that the two cases are not substantially related, the situation described involves a possible conflict of interest under Rule 4–1.9(b). To reach a conclusion whether there is a conflict, Attorney must determine whether Attorney came into possession of any information in the course of representing Client A that could be used to the Client A´s detriment in the current action.