Heres my take on this.I have testified on many cases involving bad guy shooters.Not once has the issue of ammo ever been brought up.I can't even recall hearing anything about what make of bullet was used,just the gun itself.
Gathering evidence on the type of ammunition used is standard procedure and is covered in most homicide investigation checklists. Whether the subject will come up in trial court will depend on the case.
It could come up for any number of reasons--and then again, it may not.
If this never comes up involving criminals shooting people,I really doubt it would come up in a self defense shoot that was legal and justified.Maybe it would come up if it was a bad shooting?
But the purpose of the trial is to determine if the shooting was justified. If enough evidence supports the defendant's case don't expect to hear about the ammunition.
Take the Harold Fish case, for example. Fish shot and killed someone. He was unable to present sufficient evidence to create reasonable doubt in the minds of the jurors about the charge that he committed murder in the second degree. The state introduced evidence about the factory ammunition Fish used to establish state of mind.
Was it determinative? Who knows?