> Pragmatically, criminal convictions of all individuals, race notwithstanding, requires a unanimous jury verdict.
No, pragmatically the vast majority of criminal convictions are the result of plea bargains, with no jury involved; the calculus that goes into agreeing to a plea bargain certainly includes the expectations regarding a jury verdict, but it also includes the cost of pre-trial confinement and other factors.
> In those jurisdictions with high concentration of blacks, which is where the preponderance of black crime takes place, juries would be highly likely to include black members whose assent is required for conviction of a black defendant.
It may be more likely that this is the case, but its not guaranteed. Particularly given that jury pools are not guaranteed to be representative (typically, they are determined by means like voter registration and drivers licenses, which may not be consistent in participation across races.)
> On that basis, bias against blacks would not account for population rates of convictions in those localities, at least insofar as post-arrest procedures are concerned.
You seem to be saying that jury pool considerations would prevent racial bias in post-arrest conviction rates; while that's wrong for post-charge rates for the reasons stated earlier in this comment, its even more wrong for post-arrest rates because it ignores prosecutorial bias, which introduces potential post-arrest bias in the rates of criminal charges being pursued for like conduct.
> Still, if the difference in crime rates (based on convictions) is great enough, non-jury convictions wouldn't explain it.
Upwards of 90% of US criminal cases (not just convictions, but all cases; the share of convictions -- since all plea bargains are convictions -- is even higher than the share of cases) are resolved by plea bargains [0]. There's virtually no level of disparity in total convictions that could be explained by disparity in the plea bargaining process, which is overwhelmingly how criminal convictions are arrived at.
[0] https://www.bja.gov/Publications/PleaBargainingResearchSumma...