Is a judge allowed to consider an argument not made by the plaintiff or defendant?

Small claims and administrative proceedings are set up so that parties do not require attorneys. That means the rules of procedure usually permit judges to serve more of an inquisitorial function than the purely adjudicative role of a judge in other U.S. proceedings.

Suddenly a real life case, although not criminal at all.

Scotus has already heard the evidence (and by all accounts made up its mind) on the question about citizenship on the 2020 census. Suddenly strong evidence has come up that one of the parties lied (I think committed perjury) in their arguments. Can the court use this evidence in their decision? Of course, in practice, the court can do what it likes since no higher court is available to appeal to but legally can it?

Story from years ago here in Oz. Person I knew was a freshly minted lawyer (or possibly still a student.) He got pinged by a radar speed trap. Being bloody minded he decided to fight the fine simply because he could. So he appears in court with a very bored policeman appearing for the traffic division. He basically says “I wasn’t going that fast.” with nothing more useful to say. Policeman presents the usual paperwork. Once everyone is done the judge just says, “case dismissed” To the incredulous policeman the judge says, “the calibration certificate for the radar gun has to be signed by a sergeant or above - and this one wasn’t. Case dismissed.”

*snip. I agree, and find this to be an unfair aspect of the court system. For example, if I go up against a quality attorney and we each file excellent briefs on each side of an issue: I have Smith v. Jones on my side and argue it applies, but the other attorney has Holton v. State on his side and argues equally forcefully that this case applies to the facts, I can go into oral argument and do what lawyers should do: each present our side and let a neutral judge decide who has the better of it.

If I am against a lousy attorney, I file a brief with my Smith v. Jones argument and the other attorney makes a ridiculous argument, one that is simply laughable. I then have to scour the casebooks to come up with any possible argument the judge may come up with to justify ruling for the other side because the judge sees the ridiculous argument and has to undertake his own review.

I have to prepare for anything and everything that may be thrown at me, and these system rewards attorneys for being unprepared.

That’s pretty good! It reminds me of something that happened to my wife when we lived in New York. She got a parking ticket, I forget for what. Maybe for parking against a yellow curb. She thought she had a good case that she wasn’t in violation, so she took some pictures and contested it. She went in front of the judge (I guess?) who looked at the street named on the ticket, then pulled a big book from under the desk. The judge flipped through the book, then announced, “I don’t find that street name in The Book.” The ticket was tossed out.

Mostly occurs when the plaintiff or prosecution bases it’s case upon emotional aspects, and not hard evidence. For example, when a murder is so heinous and horrible, a jury is disposed to punish somebody, and of course there’s the defendant, right there. But as you said, more often with civil cases.

That happened when I was working in San Jose. Two Hells Angels working as bouncers in a strip club, beat a man to death. The DA, for no explainable reason, went for Murder 1, only. The defense was pretty much able to show that yeah, they did beat him, and yeah, that killed him, but they never meant to. Obvious and admitted manslaughter. So they went free.
http://www.metroactive.com/papers/metro/10.23.97/pink-murder-9743.html