@Ravenmoon Hey there, good to see you again!
Exculpatory evidence is simply "evidence, such as a statement, tending to excuse, justify, or absolve the alleged fault or guilt of a defendant." See:
exculpatory evidence
An alleged confession from a third party would be exculpatory evidence and would always remain such. An alibi would obviously make the confession less likely, and thus needs to be weighed against each other to determine which is more credible. This would be a fact question for a jury.
In the instant case (meaning State v. Allen), Judge Gull must first determine whether the defense has grounds for a third-party defense.
- If the answer is "yes they do," then evidence of third-party confession is admitted, which the prosecution would rebut the exculpatory evidence with alibi evidence at trial. The jury would weigh the competing evidence, and make whatever decision they feel appropriate.
- If the answer is "No nexus for third-party defense, then any other "Odinists with verified alibis" is not relevant evidence, and thus inadmissible.
The issues of third-party defense and exculpatory evidence are obviously intertwined, and seeing the timing of the various determinations is important.
1. Make determination whether evidence is exculpatory.
2. Determine relevance of evidence (judge determines).
3. Determine any exceptions for excluding relevant evidence (judge determines).
4. Admit/Deny admission of evidence (judge determines).
5. Determine whether exculpatory relevant evidence is credible (i.e. is alleged confession reliable? Is confessor alibi reliable?) (Jury determines).
I know this is a convoluted answer, but I felt it important to show the order of determination of the issues to adequately answer you. If I didn't even come close to answering your question, I apologize. It always stays exculpatory though.
Edit: added "confessor" to alibi