A law firm can represent both parties in a matter, but only in narrow circumstances: the parties’ interests must be genuinely aligned, every client must give informed consent in writing, and the matter cannot be one of the categories where dual representation is prohibited outright. In an adversarial situation — a contested divorce, a lawsuit between the two of you, criminal co-defendants — the answer is almost always no, no matter how amicable things feel today.
The Default Rule and Why It Exists
Every lawyer owes two core duties to a client: loyalty and confidentiality. Loyalty means the lawyer fights for your interests without being pulled in another direction. Confidentiality means what you tell your lawyer stays protected. Representing both sides puts both duties under pressure. One attorney cannot aggressively negotiate a property split for one spouse while simultaneously advising the other spouse on how to protect assets. Information one client shared in confidence could end up used against them.
ABA Model Rule 1.7 captures this by defining a “concurrent conflict of interest” as any situation where representing one client creates a significant risk that the lawyer’s work for another client will be compromised.1American Bar Association. Rule 1.7: Conflict of Interest: Current Clients When that risk exists, the default is that the firm cannot take on the representation. The exceptions require clearing a high bar.
When One Firm Can Represent Both Sides
Joint representation works best in transactional settings where both parties want the same result and are cooperating to get there. Two entrepreneurs forming a business together, a buyer and seller closing a straightforward real estate deal, family members settling an estate amicably — these are the classic examples. A single lawyer can help both sides reach a mutually beneficial arrangement and save everyone the cost of hiring separate attorneys. The official commentary to Rule 1.7 acknowledges this, noting that common representation is appropriate when clients are “generally aligned in interest even though there is some difference in interest among them.”2American Bar Association. Rule 1.7 Conflict of Interest: Current Clients – Comment
Alignment is not enough on its own. Joint representation also requires informed consent, confirmed in writing, from every client involved.1American Bar Association. Rule 1.7: Conflict of Interest: Current Clients “Informed consent” is not a signature on a form. Under ABA Model Rule 1.0, the lawyer must explain the material risks of joint representation and the alternatives available, in enough detail that each client genuinely understands what they are agreeing to.3American Bar Association. Model Rules of Professional Conduct Rule 1.0 – Terminology That explanation should cover how the arrangement differs from having your own lawyer, the fact that attorney-client privilege generally does not apply between jointly represented clients, and each client’s right to consult an independent attorney before agreeing.
When It Is Not Allowed at All
Some conflicts are so fundamental that no amount of client consent can fix them. These are called non-waivable conflicts. The clearest example is representing both the plaintiff and the defendant in the same lawsuit. Rule 1.7 explicitly prohibits a lawyer from asserting a claim by one client against another client in the same proceeding, even if both clients say they are fine with it.1American Bar Association. Rule 1.7: Conflict of Interest: Current Clients The adversarial system simply cannot function when the same lawyer is arguing both sides.
The commentary goes further: whenever the relationship between the parties has already turned antagonistic, or contentious litigation is imminent, joint representation is “plainly impossible” regardless of consent.2American Bar Association. Rule 1.7 Conflict of Interest: Current Clients – Comment A divorce heading toward court, a business partnership already in dispute, neighbors trading demand letters — one firm cannot handle both sides.
Criminal Co-Defendants
Criminal cases add a separate constitutional layer. The Sixth Amendment guarantees every criminal defendant the right to effective, conflict-free counsel. This is not just an ethical rule — it is a right that courts are obligated to protect.4Congress.gov. Amdt6.6.5.1 Overview of the Right to Effective Assistance of Counsel The Supreme Court has described the right to counsel as “too fundamental and absolute to allow courts to indulge in nice calculations as to the amount of prejudice arising from its denial.”5Justia Law. Holloway v. Arkansas, 435 U.S. 475 (1978)
In practice, a trial judge can refuse to let co-defendants share a lawyer even when both defendants want to. In Wheat v. United States, the Supreme Court held that trial courts have “substantial latitude” to reject conflict waivers in criminal cases and insist on separate representation, not only when an actual conflict exists but whenever there is a “serious potential for conflict.”6Library of Congress. Wheat v. United States, 486 U.S. 153 (1988) If a trial court forces joint representation over a lawyer’s objection that a conflict exists, any resulting conviction is automatically reversed.5Justia Law. Holloway v. Arkansas, 435 U.S. 475 (1978)
What Happens If the Arrangement Falls Apart
This is where most people underestimate the risk of hiring one firm for both sides. If a real conflict develops after the joint representation begins, the lawyer typically must withdraw from representing everyone, not just one side. The ABA commentary is blunt: “if the common representation fails because the potentially adverse interests cannot be reconciled, the result can be additional cost, embarrassment and recrimination.”2American Bar Association. Rule 1.7 Conflict of Interest: Current Clients – Comment Both clients then have to find new lawyers, get them up to speed, and start over. The efficiency that made shared representation attractive disappears.
Former Clients and Prior Consultations
Conflict rules do not expire when the attorney-client relationship ends. Under ABA Model Rule 1.9, a lawyer cannot represent a new client against a former client in the same matter, or in any substantially related matter, if the new client’s interests are adverse to the former client’s, unless the former client gives informed written consent.7American Bar Association. ABA Model Rules of Professional Conduct – Rule 1.9 Duties to Former Clients Two matters are “substantially related” when they involve the same transaction or when confidential information from the earlier case could be used against the former client. A lawyer who learned a business owner’s financial details during a corporate matter could not later represent that owner’s spouse in a divorce.
This protection also reaches people who consulted with a lawyer but never hired them. Under ABA Model Rule 1.18, if you sit down with a lawyer and share information about your case, that lawyer cannot later represent someone with adverse interests in the same matter if the information you shared could significantly harm you.8American Bar Association. Rule 1.18: Duties to Prospective Client Be thoughtful about how much you disclose in an initial consultation.
When the Whole Firm Is Disqualified
A conflict belonging to one lawyer does not stay with that lawyer alone. Under ABA Model Rule 1.10, if any lawyer in a firm is personally disqualified from a matter, every other lawyer in the firm is generally disqualified too.9American Bar Association. Model Rules of Professional Conduct Rule 1.10 – Imputation of Conflicts of Interest: General Rule A firm cannot sidestep the rules by handing the case to a different partner down the hall. So if you learn that a firm has ever represented the other side in a related matter, the conflict likely reaches the whole firm, not just the specific attorney who worked on it.
There is a limited exception when a lawyer moves between firms. A new firm can continue representing its client even if a lateral hire brings a conflict, provided the incoming lawyer is “timely screened” from the matter, receives no share of the fee, and the former client gets written notice describing the screening procedures.9American Bar Association. Model Rules of Professional Conduct Rule 1.10 – Imputation of Conflicts of Interest: General Rule The former client can request certifications at reasonable intervals confirming the screen is being maintained.
What to Do If You Think There Is a Conflict
Start by raising the issue directly with the lawyer. Ask specifically whether the firm represents, has represented, or has any connection to the other parties, and whether anyone at the firm has a personal or financial stake in the outcome. Many conflicts surface because the firm failed to run a proper check at intake, and a direct question resolves the issue quickly.
If the answer does not satisfy you, consult an independent attorney. A second lawyer can evaluate whether an improper conflict exists and advise you on whether it is the kind that can be waived with your informed consent or the kind that requires the firm to step aside entirely.
In active litigation, you or your new attorney can file a motion asking the court to disqualify conflicted counsel. Courts take these motions seriously because the integrity of the proceeding depends on both sides having unconflicted representation. If the conflict is egregious, a court may disqualify the lawyer on its own initiative.
You can also file a complaint with your state’s bar disciplinary agency. Each state has its own body that investigates ethical complaints and can impose discipline ranging from a private reprimand to suspension or disbarment.10American Bar Association. Resources for the Public If a conflict has caused you actual harm — a lower settlement, unfavorable deal terms, a weakened case — you may also have a legal malpractice claim, though proving malpractice requires showing the conflict itself caused the loss, not just that it existed.