Are judges limited in their reasoning to arguments raised by the parties?

Question

Bob files a civil lawsuit agaist Rob. For simplicity, let's assume they both represent themselves.

At the hearing, Bob says: "Here is the evidence. Rob was wrong because of reason A, so he owes me money."

Rob replies: "Yes the evidence is true, but because of reason B reason A does not apply. I do not owe Bob anything."

Bob has nothing to add.

The judge proceeds making a judgment. Let's consider three alternatives:

1. He simply agrees with Rob: reason B indeed negates reason A. No questions here.
2. "Here is reason C why reason B in these circumstances does not actually negate A as Rob contends, so Rob still owns money to Bob."
3. "Reason B does indeed negate reason A as Rob contends. However, notwithstanding with that, here is reason D why Rob is nevertheless at fault, so he owns money to Bob."

In adversarial common law jurisdictions, will judgements 2 or 3 be inappropriate for a judge to make? Are there rules in place that forbid judges from making judgements like either 2 or 3?

As a very simple example, the above reasons A, B and C can be instanced this way:

• Bob's A: "Rob went on red light so he is liable"
• Rob's B: "Yes I did, but that was right turn, which is allowed there"
• Judge's C: "Right turn on red is indeed allowed there but not on Sundays when the incident happened, therefore Rob is liable".

Clearly, reason C was not raised by either party. Will the judge be allowed to not present it to Rob before delivering it in judgement?

This question has been induced by some statements made in feedback to this question:

By @phoog:

Courts generally cannot consider arguments that aren't raised by a party in the case.

By @Tim Lymington:

It would clearly be unfair (as phoog says) for the judge to base his judgment on his own research without giving either counsel a chance to consider it

So, how do those statements stand when judge, merely applying the law, can't help generating a new argument that neither of the parties thought of?

Closely related: If a judge constructs arguments for the prosecution in judgment is that grounds for appeal?

Answer 1

Yes

Deciding a case on a basis the parties have not raised is a denial of natural justice (or procedural fairness) and invalid.

The reason is very simple, the parties have not had the opportunity to produce evidence or make submissions about C or D that might have changed the judge’s mind about them. Notwithstanding, to successfully appeal, the aggrieved party must show there were arguments that could have been raised which could reasonably have altered the outcome.

That said, it’s the judge’s courtroom and they can say “That’s interesting but what about C and D?” and then the parties can make submissions about them. They do have to be circumspect and make sure that they do not become one party’s advocate - one party might be well aware of C and D and don’t want them brought up because they damage their case and they are hoping the other party misses that - and then the bloody judge come charging in with his bloody duty to wider interests of justice.

Non-judicial decision makers like arbitrators, adjudicators and other tribunals need to be even more circumspect because they generally don’t have a duty to anyone but the parties.

Unlike in civil law systems, the role of the judge is to decide the dispute between the parties as a referee, not to determine some objective”truth” as an investigator.

To keep things simple: if the plaintiff contends that the light was red and the defendant contends the light was green then, assuming there is no evidence opening the possibility, it is not open to the judge to find that the light was amber. Similarly, if the parties agree that red means go and green means stop, it is not the judge's role to tell the parties they are wrong (I'm sure questions would be asked but if the parties are adamant ...): since there is no dispute over this issue the judge would be wrong to agitate one.

Now, a judge is free to apply the law that was argued as a whole - if arguments centred on Section 14 of the Relevant Act 1875 but Section 15 is applicable and germane the judge is not wrong for applying Section 15. However, they are on shakier ground if the bring in Other Slightly Relevant Act 1956.