The Department of Homeland Security (DHS) and the Department of Justice (DOJ) recently released a report on immigrants incarcerated in the federal Bureau of Prisons (BOP) and as pretrial detainees by the U.S. Marshals Service (USMS). The report offers some comments on state and local incarceration of non-citizens, but no systematic information. BOP and USMS are both agencies within the DOJ, so it is simpler to look at the numbers for the DOJ altogether.

The DHS and DOJ are two agencies charged with enforcing immigration laws and incarcerating those who violate them, so it is unsurprising that a large percentage of those incarcerated in federal prisons are there for violating immigration offenses. According to the report, about 19 percent of those incarcerated in the BOP or held by the USMS are known or suspected illegal immigrants and about 6 percent are legal non-citizens. The remaining 75 percent are U.S. citizens, but some unknown percentage of them are likely immigrants too. Non-citizens are about 7 percent of the entire U.S. population so they are overrepresented in federal prison.

The report breaks down the primary offenses that non-citizens are incarcerated or held for in federal custody. The most common primary offense was immigration at 38 percent, followed by drug offenses at 37 percent. Other crimes comprise the remaining 25 percent. The report does not show the number of primary offenses committed by illegal immigrants. Through the 3^rd quarter of 2018, about 33.7 percent of new offenders were sentenced for immigration offenses according to the U.S. Sentencing Commission. Turns out that non-citizens are more likely to be sentenced for immigration offenses, which is not surprising.

More importantly, the federal prison population and those held by the USMS are not representative of incarcerated populations nationwide, so excluding them from the report means that it sheds little light on nationwide incarcerations by nativity, legal status, or type of crime. Of the roughly 2.3 million people incarcerated in 2018, only about 8.3 percent were in federal prisons or held by USMS while the rest are in state and local facilities.

Federal crimes are also vastly different from state crimes, so the criminals incarcerated in the federal system are very different from those on the state level. Through the 3^rd quarter of 2018, 50,929 people were sentenced to federal prison for federal crimes – 33.7 percent for immigration crimes. Those immigration convictions comprised 100 percent of the convictions for immigration crimes in the United States in 2018 through the 3^rd quarter. By contrast, there were only 94 federal convictions for murder or manslaughter during the same time. Although the data for murders in 2018 are not released yet, those federal murder convictions will likely account for less than 1 percent of all murders nationwide if past years are any guide. For instance, if Mollie Tibbets accused killer is convicted then he’ll be in state prison and not counted in the federal homicide conviction statistics.

It’s important to understand the number of crimes caused by illegal immigrants, their criminal conviction rates, and their incarceration rates. But doing so requires examining state-level data in addition to federal data so looking at only the latter produces a non-representative and inaccurate picture of the problem. Based on the limited evidence that we have, illegal immigrants are less crime-prone than native-born Americans but more crime-prone than legal immigrants.