Can a judge decide a case based on their own legal knowledge?

Question

Can a judge in the United States decide a case based on their own legal knowledge, using some legal theory or argument that was not presented by either side in the case, which neither side therefore had the opportunity to challenge? In other words, could a judge decide a case in a way that neither side argued for? Are there any important cases where this has happened?

Answer 1

Can a judge in the United States decide a case based on their own legal knowledge, using some legal theory or argument that was not presented by either side in the case,

Yes.

which neither side therefore had the opportunity to challenge?

In theory, this can be problematic and the better practice is to ask the parties to brief a new issues the court wants the parties to consider before ruling.

But since motions to reconsider filed promptly after a judge rules are allowed in most courts, a true denial of an opportunity to challenge is fairly rare.

Mostly, the harm involves denying the parties an opportunity to preserve legal issues for appeal, which motions to reconsider can address. But of course, if the judge's ruling was legally correct, the appeal would fail anyway.

In other words, could a judge decide a case in a way that neither side argued for?

Yes.

Are there any important cases where this has happened?

Yes.

I'll try to think of some examples of high profile cases where it has happened and cite to them. I can recall, for example, that this happened in some SCOTUS cases on jurisdiction and pleading rules, although it isn't that rare in the appellate context either.

It has also happened in a fair share of cases I've personally litigated. It probably happens at least once every year or two in a busy litigation practice.

Answer 2

Courts are bound to decide on the basis of the evidence introduced into the trial. This limits their creativity: The parties usually are aware of the legal implications of the evidence and bring the corresponding arguments. If the judge sees something both parties are missing, he or she will usually start asking pointed questions which alert the parties. It would be odd to make a "secret" and lone decision without hearing arguments about its merits, and a controversial surprise decision would likely not survive an appeal.

The situation is somewhat different with the Supreme Court because they interpret the slow-changing constitution in a fast-changing world. The Supreme Court has also considerable and unusual freedom because there is no appeals court; any decision it delivers stands. Obviously, its interpretation of the constitution has changed over the centuries, but usually as a result of being asked by one of the parties.

On occasion, though, the Supreme Court has been accused of overreach, from both sides of the aisle. Of particular interest here are cases where the decision went further than the interested party actually requested. This paper discusses four such rulings. I believe that the introduction describes your scenario (emphasis by me):

When the Court decides its own questions, rather than those presented by the parties, it does so without the benefit of a record created below on the question, without the opinions of lower court judges, and sometimes without the briefing of the issue by the parties or amici.

Answer 3

This is not a too infrequent occurrence at probable cause hearings. The prosecution is supposed to convince the judge there was sufficient evidence to arrest the suspect at the time without a warrant.

When there is no evidence judges can and do release the suspect - this most frequently happens when actual charge should be contempt of cop, and is an example of the process is the punishment. Judges practically never go beyond finding no probable cause, so the prosecutor and cop both get away with betraying their oath.

It is arguable whether this is deciding a case, as charges can still be brought, but typically aren’t.