The former case results in GP's tie, the latter in the absurdly skewed prison population the US is known for.
People are horrible at logical thinking.
Are you sure? Since most homicides are intra-racial [1] (despite the impression one gets from those the media choose to focus on), we can use victim race as proxy for offender race (I'd use offender race directly, but then you'd just blame it on police racism). Since it's hard to manufacture a corpse, or fake its race, we can further assume that data is largely free of police bias.
So white+Hispanic are 50% of homicide victims [2] (which we use as proxy for perpetrators), and 58% of the prison population [3]. For blacks, its 44% and 37%, respectively. Doesn't look particularly skewed to me. There is some anti-white+Hispanic bias, but since we're looking only at homicide to avoid police bias, we're not seeing the whole picture, which may explain the disparity.
[1] In approximately ninety percent of all murders committed in the U.S. over the years, the victim and perpetrator are of the same race - https://www.psychologytoday.com/us/blog/wicked-deeds/201602/...
[2] https://ucr.fbi.gov/crime-in-the-u.s/2019/crime-in-the-u.s.-... (for some reason the FBI groups whites with Hispanics)
[3] https://www.worldatlas.com/articles/incarceration-rates-by-r... (white and Hispanic are again grouped)
This is not supported at all. I assume you're talking about racial demographics of prison population. It's a complex historical and socioeconomic problem, biased juries may have some role but it wouldn't be on the top 10 factors.