Rule 1.9 on former clients and confidentiality: why informed consent matters

Confidentiality isn’t just a checkbox in a code. It’s the bedrock of trust between a lawyer and a client. When the relationship ends, that trust isn’t magically sealed in a drawer. Rule 1.9 of the Model Rules of Professional Conduct keeps the lock on confidential information even after the last memo has been filed and the last depositions taken. So, what does this mean in plain English, especially when we’re thinking about former clients?

Let’s cut to the chase: the right answer to the question about former-client confidentiality is that a lawyer must obtain informed consent to use information related to the former representation. In other words, you can’t casually reuse a former client’s confidences or strategies just because the relationship has ended. You need the client’s informed consent, ideally in writing, before any such information is used for a new matter or disclosed in a way that could affect the former client.

Rule 1.9, in plain terms

Think of Rule 1.9 as a shield around information that was shared in confidence during the prior representation. The rule says that, once the attorney-client relationship ends, a lawyer generally cannot use or disclose information related to that representation to the former client’s disadvantage, unless the former client gives informed consent confirmed in writing. It’s not about whether the lawyer still “knows” the information; it’s about whether that information—confidences, strategies, or facts learned in the course of representation—may be used against the former client or in a way that could be harmful without consent.

This isn’t a license to spill the beans or brag about your old cases. It’s about protecting the client’s control over their own information. The client should decide if and when their information is ever reused, and how it’s shared.

What counts as “information related to the representation”?

Here’s the tricky part that trips people up in seminars, clinics, and even in real life. Information related to the representation isn’t just state secrets or jaw-dropping tactics. It includes:

• Confidential communications between attorney and client.

• Opinions, approaches, or strategies formed during the representation.

• Facts learned in the course of representing the client, if those facts were kept confidential.

But not everything a lawyer knows is off-limits forever. Information that wasn’t obtained through the representation, or information that is already public, can sometimes be used without the same consent requirements. And if the client waives the protection in writing, consent can be given—though that waiver should be clear and voluntary.

When is consent required?

Consent is required whenever you want to use information related to the former representation in a way that could be adverse to the former client, or in a new matter where the information might be helpful to the new client or to the lawyer’s own understanding. The key is informed consent, ideally documented in writing. It isn’t enough to say, “You signed off on it earlier,” or to expect a vague nod. The client must understand what information is being used, for what purpose, and the potential implications.

A quick reality check: the common-sense rule

• You can’t assume it’s okay to reuse old confidences just because the client’s no longer a current client.

• If you wouldn’t want someone to reveal your own private details in a different matter, don’t reveal your former client’s without consent.

• If the information is public or not tied to the former representation, you may have more leeway, but it’s still wise to tread carefully and seek counsel when in doubt.

A few real-life scenarios to illustrate the point

• Scenario 1: You represent Client A. After the matter ends, Client A faces a different lawsuit. You want to reference a confidential strategy you learned while representing Client A to bolster your argument for Client B. Without consent, that’s a no-go. Even if the information seems general, the risk is that it’s rooted in confidential knowledge from the prior representation.

• Scenario 2: During a speaking engagement, you mention a case study from a former matter. If those details were confidential, you’d be crossing the line unless you obtain informed consent in writing from the former client. Even anonymizing doesn’t automatically solve the issue if the details could reasonably reveal confidential aspects.

• Scenario 3: You rely on a publicly known fact from the prior representation (for example, a public court ruling) to support an argument for a new client. That information is different—it's not confidential and can be used—but you should avoid presenting anything that could be traced back to confidential matters without consent.

The subtle but critical point: honesty and integrity

Confidentiality isn’t just procedural; it’s a signal to clients that they can speak freely, knowing their confidences stay protected. If lawyers routinely reuse confidential information without consent, clients won’t feel free to be candid. The legal profession sustains itself on trust, and Rule 1.9 is a constant reminder of that trust’s fragility.

Practical tips for staying on the right side of Rule 1.9

• Create a standard practice for handling former-client information. When a matter ends, move confidential files to a secure archive and separate any notes that contain client confidences.

• Don’t reuse notes or memos without evaluating whether they contain information tied to the prior representation. If they do, you need consent from the former client.

• If consent is appropriate, get it in writing. A simple, clear consent form can prevent a lot of headaches later.

• When in doubt, seek ethics counsel. It’s better to check now than face a later claim that you mishandled confidential information.

• Consider whistle-blowing or redirection: if you’re in a firm with multiple practice areas, have someone independent review whether any information from a former matter could be used in a new matter.

• Keep a habit of documenting: who approved the use of any former-client information and under what terms private and secure.

Why this matters beyond the exam hall

People hire lawyers because they trust us with sensitive details. If that trust erodes, clients may hesitate to share critical facts in the future. That’s not a hypothetical concern—it affects real outcomes, from settlement discussions to courtroom strategies. The confidentiality shield is what makes a lawyer-client relationship viable in the first place. It’s not a relic of the past; it’s a living standard that guides daily decisions.

Key takeaways you can carry forward

• Rule 1.9 centers on confidentiality for information related to the former representation.

• Before using any such information in a new matter, obtain informed consent in writing.

• The mere end of a relationship doesn’t erase the duty; it often deepens it.

• Distinguish between confidential information and public knowledge, and tread carefully with anything that could be traced back to the prior representation.

• Build systems in your firm to separate and protect confidential information after matters close.

A final thought on the ethic landscape

Ethics isn’t a list of rigid rules you memorize and forget. It’s a living framework that helps lawyers protect clients and preserve the profession’s integrity. Rule 1.9 is a clear, practical reminder: the confidence you earn from a client isn’t something you can casually disassemble once the case wraps up. If you treat that confidence with care, you’ll not only stay compliant—you’ll also build a practicing life where clients feel truly seen and protected.

If you want to explore this topic further, the Model Rules and accompanying ethics opinions from bar associations are solid, reliable places to look. They offer scenarios, commentary, and practical guidance that can ground your understanding when facts get fuzzy. And yes, it’s worth your time to keep a thoughtful eye on how confidentiality travels from one matter to the next—because trust, once earned, is the quiet force behind every successful legal outcome.