arentol, while the situation in particular was not the same, the issue was the permissibility of defense expert witnesses being allowed (or not) to testify about the GSR results from tests of Bias's handloads.
How could this come up in a self-defense scenario? Let's say we have a he-said / he-said shooting. The shooter claims self-defense, and says the aggressor was charging him with a knife. He shot when the guy was very close; the shootee says, no, I was nowhere near that close, and I was not attacking him.
GSR shows less than expected for the range the shooter claims.
Prosecution witness says the GSR indicates that the shootee's story is the correct one.
Defense witness can't testify that the shooter's handloads burn cleaner, and produce less GSR, because rules of evidence won't allow testing of evidence that was manufactured by the defendant. Even though the witness might run multiple tests that show the defendant's loads produce that low GSR result at the range the defendant claims, the judge might never allow that into evidence.
So Bias doesn't bear directly on self-defense, but its implications for rules of evidence do have some bearing.