From WILLIAM LAFFERTY:
Hand loading or factory loading of the projectile that killed the criminal is irrelevant to the question of whether the shooting was justified.
Yes, that's true, but that is not the issue.
So--a shooting has occurred, and the shooter effectively admits to having fired the shots by claiming self defense.
It's now up to the charging authority and if it goes further, to later authorities, including perhaps a trial jury, to judge whether or not the use of deadly force was justified.
The shooter will produce whatever evidence he can to substantiate that all of the necessary elements of a self defense claim apply. Depending on what else investigators may have found, in terms of forensic evidence, eyewitness testimony, information about the shooter and possible relationships with the person he shot, or anything else about the shooter that may pertain to motive,
mens rea, etc., investigators and potentially, prosecutors, will produce
their evidence. Each side will try to discredit the evidence produced by the other--again,
if it goes that far.
Now, if at any stage from the beginning of the investigation to a possible acquittal, it is determined that the shooting was justified, it doesn't matter whether the shooter used a handgun or a flare gun, as far as justification is concerned, and as you pointed out, hand loading or factory loading of the projectile that killed the criminal is irrelevant to the question of whether the shooting was justified. But again, that's not the issue.
The issue is whether or not it is the shooter who is judged to be "the criminal", and that has to be determined from the evidence. Though the likelihood is probably remote, the use of handloads can influence that determination. There are two ways;
The first, to which Massad Ayoob attaches comparatively little importance in comparison with the second, is the possibility that,
in combination with other evidence, the selection of a highly destructive load (and this can of course also apply to certain
factory loads or chamberings, as in the Harold Fish case) is seen as indicative of a criminal state of mind, or of a propensity to shoot someone. This would only be important if the evidence of justification were inconclusive in comparison with evidence unfavorable to the shooter. By the way, mock jury simulations have shown that the use of assault-type guns in shootings can reduce a shooter's chances of a finding of justification, in comparison with scenarios in which more "traditional" guns are used.
The second has been addressed numerous times in this string, most recently by Fiddletown:
...there may be times when it will be desirable to be able to use GSR evidence to help establish or corroborate a point useful in your defense. For example, if you testify that you fired the shot when the alleged assailant was at a distance of X feet; and if there's some dispute on that point, it would be useful to test exemplar ammunition under similar conditions. Hopefully the test results will then show similar GSR traces and be admissible as evidence to support your testimony. But of course, it will only be admissible if an adequate foundation can be laid establishing that the test duplicates in all material respects the event that is the subject of the trial.
Depending again on how the evidence produced by the defendant stacks up against potentially contradictory evidence presented by the state, the distance at which the shot was fired may become critical to the defense, for two reasons: (1) it could enter into the judgment of whether the shooter actually had reason to believe that imminent danger existed and (2) the state's evidence showing a difference between the distance involved and what the shooter had previously said it to be could seriously damage his credibility. GSR evidence is routinely used to try to establish shooting distance. The lack of GSR on a subject may indicate a greater distance than the subject has claimed, and test evidence may support his testimony.
So, yes, the load is not at all relevant to whether the shooting was justified --it's just in getting to that determination in combination with all of the evidence that it just might make a difference.
I hope that helps.