The Expert Used to Wear a Robe. The Jury Still Has Only One Judge.
A retired federal appellate judge can bring decades of specialized experience into a courtroom. She cannot bring a second set of jury instructions. On October 9, Corcept Therapeutics asked a federal court in California to exclude an expert report by retired Federal Circuit Judge Kathleen O'Malley in an antitrust case brought by Teva. According to Corcept, the report does not apply technical expertise to disputed facts. It tells the factfinder that Corcept's earlier patent cases were sham litigation. Teva has not publicly answered the motion, O'Malley has not commented, and the court has not ruled. Those limits matter. So does the problem the motion exposes: the more authoritative an expert appears, the more carefully a court must separate useful experience from an opinion about what the law means and who should win.
The dispute is about role, not résumé
Teva sued Corcept in 2024, alleging that Corcept used patent litigation to delay generic competition for Korlym, a treatment for Cushing's syndrome. Corcept denies the allegations. The case remains pending, and no court has found antitrust liability. Teva retained O'Malley, who served on the Federal Circuit from 2010 until her retirement in 2022, as an expert on patent litigation practice.
Reuters reports that Corcept's motion challenges her conclusion that its earlier patent suits were objectively baseless and therefore sham litigation. Corcept says those are legal conclusions, not technical opinions, and that jurors may give them unusual weight because they come from someone who once decided patent appeals from the bench. The motion also says she lacks scientific or pharmaceutical expertise relevant to the underlying patents.
That argument should not be mistaken for a rule that judges may never testify as experts. A former judge can possess specialized knowledge about patent procedure, court practice, or the institutional mechanics of litigation. The title does not disqualify the witness. It also does not expand the witness's permitted subject. Qualification answers whether the person knows something useful. It does not answer whether the proposed opinion belongs to the witness, the trial judge, or the jury.
The line matters in any case that uses lawyers, former regulators, compliance officers, or judges as experts. Legal experience can illuminate how a specialized system works. It can also make a conclusion sound binding when it is only one side's retained opinion.
Rule 704 does not mean anything goes
Federal Rule of Evidence 704(a) says an otherwise admissible opinion is not objectionable merely because it embraces an ultimate issue. That language ended an older and often artificial prohibition. A doctor may opine about causation. An accountant may trace funds. An engineer may explain why a failure occurred. The opinion does not become inadmissible simply because it bears directly on a question the jury must resolve.
But Rule 704 is not a freestanding admission rule. The opinion still must satisfy Rule 702. The proponent must establish, more likely than not, that specialized knowledge will help the factfinder, that the opinion rests on sufficient facts or data, and that reliable principles and methods were reliably applied. Repeating the requested verdict in legal language is not a method.
The Ninth Circuit drew the distinction in United States v. Diaz. An expert may address an ultimate factual issue, but cannot give an opinion that amounts to a legal conclusion or tell the jury the result to reach. The problem is not that the testimony is important. The problem is that it answers a question the legal system assigns to someone else.
That boundary is less tidy than the slogan suggests. Lawyers and experts often work in fields whose ordinary vocabulary overlaps with legal standards. Reasonable, material, control, duty, causation, and deception can be facts, industry terms, or legal conclusions depending on how they are used. Courts therefore have to examine what the witness actually did, not perform a search for prohibited words.
An expert can describe the terrain without deciding the case
A useful expert makes specialized facts legible. In a patent case, that may include how claims are prosecuted, what information a practitioner would ordinarily review before filing, how infringement contentions develop, which procedural options existed, and how the challenged conduct compared with established practice. Those opinions give the factfinder tools it did not already possess.
The Ninth Circuit's decision in Nationwide Transport Finance v. Cass illustrates the divide. The court upheld exclusion of testimony that explained the law, defined the parties' rights and duties, and labeled conduct wrongful. It permitted testimony about industry conditions, standards, practices, and norms. The difference was functional. The witness could explain the commercial setting. The witness could not become the source of governing law.
That is the better way to draft a report. State the record examined. Identify the specialized practice. Explain the method used to compare the record with that practice. Describe the similarities, departures, and limits. Then stop before converting those findings into the legal conclusion reserved for the court or jury.
The discipline also improves cross-examination. A lawyer can test sources, assumptions, selection criteria, counterexamples, and application. There is very little to test when the report leaps from a chronology to the word sham. The legal label sounds decisive precisely because it conceals the intermediate work.
A former judge creates an additional authority problem
Every expert arrives with credentials. A former judge's credentials are different because jurors have been instructed to accept legal guidance from the person in the robe. When another former holder of that office appears as a paid witness and uses the language of a ruling, the risk is not merely ordinary persuasion. The jury may hear borrowed judicial authority.
Rule 403 gives courts a separate tool to address evidence whose probative value is substantially outweighed by unfair prejudice, confusion, misleading the jury, delay, or waste. A prestigious résumé is not unfair prejudice by itself. Still, a court can sensibly ask whether the same specialized information could be presented without making one advocate's legal theory sound like an appellate disposition.
The answer should not be a categorical exclusion of former judges. That would waste genuine expertise and create a status rule the evidence code does not contain. The response should be tighter scope. Limit testimony to matters requiring specialized knowledge. Bar legal instruction and opinions that simply pronounce a claim established. Use a clear limiting instruction where the residual risk can be managed. Remove honorific theater that adds status but no substance.
Counsel retaining a former judge should anticipate this problem before the report is written. The engagement letter, questions presented, report headings, and direct examination should emphasize method and experience rather than adjudication. If the value proposition is that a real judge agrees with the client, the assignment has already gone wrong.
The more impressive the expert, the narrower the lane
Corcept's motion may succeed, fail, or produce a narrower compromise. The court could exclude the challenged conclusions while allowing testimony about patent-litigation practice. It could find that the report applies specialized experience to facts without usurping the judge or jury. Until the briefing is complete and an order is entered, advocacy should not be confused with a holding.
The dispute nevertheless presents a useful rule for trial lawyers. Expertise is not a license to collapse fact, method, and conclusion into one authoritative sentence. The expert's job is to give the factfinder a disciplined way to understand evidence outside ordinary experience. The judge states the law. The jury, when there is one, applies that law to the facts it finds.
That allocation can feel inefficient when the proposed expert has already spent years deciding similar cases. It is also the point. A retired judge may know the terrain better than almost anyone in the room. In a new case, however, she is a witness. The jury still has only one judge.
A former judge's experience may qualify the witness. It does not transfer the court's authority to the witness stand.
Sources and further reading
Primary and industry sources used to support this page. External guidance should be reviewed in context and for your jurisdiction.
- Reuters, Corcept seeks to bar retired judge's viewsOctober 12, 2026 report on Corcept's October 9 motion, the challenged opinions, the parties' positions, O'Malley's background, and the pending posture.
- Federal Rule of Evidence 702Current rule governing qualification, helpfulness, sufficient facts or data, reliable principles and methods, and reliable application.
- Federal Rule of Evidence 704Current ultimate-issue rule, which removes a categorical objection without displacing the other admissibility requirements.
- Federal Rule of Evidence 403Current rule permitting exclusion when specified risks substantially outweigh probative value.
- United States v. DiazPublished Ninth Circuit decision distinguishing admissible ultimate-issue opinions from impermissible legal conclusions.
- Nationwide Transport Finance v. Cass Information SystemsNinth Circuit decision distinguishing testimony on industry practices and norms from legal instruction and opinions on rights, duties, and wrongdoing.
- Teva Pharmaceuticals USA Inc. v. Corcept Therapeutics Inc. docketPublic docket summary identifying the case, filing date, court, and case number.