This is just FEDERAL custody. What about the State prisons?
The states would never ever cooperate with some sort of federal mandate that they conduct such a study. They would scream from the rooftops that such an imposition would be cruel, racist, xenophobic. But it is exactly the type of thing that Trump should demand in the wake of this Federal report as a way to get States to scream about how they are being forced to collect data on people in their prisons.
I consider it very likely that the percentages of Illegal Alien Prisoners in state prisons is similar to that in Federal prison.
I remember reading a policy paper published in a book that said that a greater percentage of prisoners in the NY penal system were illegal aliens than Black (note these are not exclusive categories) and I believe the research was done before 1994.
Re: “What about the State prisons?”
Many states just turn over criminal aliens to the Feds.
The California “Sanctuary” state prison system has a large percentage of illegals who have been convicted on state crimes - from memory, like one third illegals.
Also, many states just release criminal aliens and give them a court date, even for violent crimes.
Here in Washington state, at least 50% of our “Ten Most Wanted” criminals consistently have Hispanic names, even though just 12% of our state population is Hispanic. Usually, they just don’t show up for trial, or they skedaddle back to Central America.