“The basic claim is at best unsustainable or more likely pure fiction. A fact created out of thin air,” Ramiro Martinez, a criminal justice professor at Northeastern University, told PolitiFact.

The bottom line, PolitiFact says, is that it’s unclear just how many undocumented immigrants are currently in prison, because the available statistics don’t provide details about inmates’ immigration status.

Analysts on both sides of the immigration debate do agree on one thing: There’s a lack of good data about this. But as to how likely it is for immigrants to commit crimes, that depends on who you ask.