I blogged about this back in 2002, but I thought I'd mention it again; it's one of my favorite simple statistics puzzles. The federal Sentencing Commission provides a table breaking down all sentenced federal offenders, broken down by offense type and race. The race categories are White, Black, Hispanic, and Other. (I realize that demographers generally view Hispanic as an ethnicity, not a race, but the Commission follows the more common lay usage here.)
For sexual assault, 51.3% of all offenders are "other." Among the U.S. public as a whole, probably only about 6% would fall into the "other" category (subject to some uncertainty that's not relevant here, since any estimate would be far below 51.3%). What's up? I'll post the answer to the comments in a few days, if no-one else gets it before then (though I suspect they will).
Since American Indians make up the virtually exclusive residents of Indian Reservations (and East Asians would include residents of places like Guam, which I believe is a federal protectorate and therefore has a district court) it's only natural that they be the perpetrators of a majority of sexual assault cases prosecuted in federal court.
Mixed-racial
Asian
Native American
Unknown
Dave
Supportive of this are the comparatively high "other" rates for assault and burglary / breaking-and-entering, which also presumably would remain uncleared at high rates. I'm not sure why manslaughter would have such high "other" rates, too, although the very small absolute numbers (5, 4, 5 in the racially identified category, 34 in the "other" category) is I suppose consonant with the unsolved-crimes hypothesis.
But John Jenkins makes an interesting case, too. Eh, I'll wait till Professor V gives the answer. (And if his response is "This might shock you but you're -both- right," I'm leaving....)
You can see which crimes typically fall under federal jurisdiction from the numbers, such as trafficing of illegals and narcotics. I also note that federal firearms prosecutions are high as well, probably as part of that ashcroft program whose name slips my mind.