From the Mouths of Babes - Evidence Rule 613 vs. 801(d)(1)(A)
So I've relearned where that came from.
Impeachment using prior inconsistent unsworn statements comes in under Rule of Evidence 613, and can only be used as impeachment evidence, not as substantive guilt/innocence evidence.
Impeachment using prior inconsistent sworn statements comes in under Rule of Evidence 801(d)(1)(A), and can be used both as impeachment evidence, and as substantive guilt/innocence evidence.
(For non-lawyers), a jury may be required to consider evidence only for certain reasons. For example, if a witness has made other statements before trial (like in a police report) and the witness says something different in trial, the witness can be impeached by their prior inconsistent statement (in the police report) However, that inconsistency can only be used to show that the witness shouldn't be believed; it cannot be used to prove (or rebut) that what the witness says happened before really happened. The prior inconsistency is not "real" or substantive evidence that a jury can use to determine guilt or innocence.
However, as a matter of practice, once a jury hears something, the jurors will use that evidence for whatever they want to use it for. This is one reason why defense attorneys don't often have their clients testify when the clients have felony convictions - although the jury will be instructed that they can only use the fact of the prior conviction to gauge the defendant's credibility as a witness, juries will often use the prior convictions to find the person guilty because he or she is a bad person.
Our jury instructions provide only for Rule 613 impeachment by prior inconsistent statement instructions, so the jury is instructed that they cannot use the impeachment evidence for their guilt/innocence determination - I need to make sure I ask for a modification for prior inconsistent sworn statements.