The first sentence of Ms. magazine's review of Silja J. A. Talvi's Women Behind Bars: The Crisis of Women in the U.S. Prison System induced my skepticism: "NHI, or no humans involved, is police jargon for the morgue remains of women prostitutes and African Americans." I found it improbable that police officers -- some of whom are themselves women and/or people of color -- would have a widespread term that reduced others of their race and sex to nonentities. However, it's a real and apparently well-known term among those involved in law enforcement.
There's an innocuous way to see the phrase, as in a recent local news item on police jargon: "A great cop phrase is, 'NHI.' This means 'no humans involved.' Cops use it when they are dealing with insignificant matters." It's also been applied to male as well as female prostitutes, and to whites perceived as part of the underclass. From what I have seen, the phrase is most frequently connected with the killings of 45 women in San Diego from the mid-1980s through the early 1990s: a public art project about the serial murder; a police officer writing about his experiences (and other cops' referring to the slayings as "misdemeanor murders"); a feminist work about violence against women.
The offensive use of "No Humans Involved" to signify the speaker's low opinion of people isn't peculiar to police, either. Earlier this year, Judge Charles Greene of Florida's 17th Judicial Circuit (Broward County) roused controversy by telling a prosecutor not to feel badly about a jury's not-guilty verdict, because the attempted murder had been of a minority and thus "N.H.I." His request to be reassigned from the criminal to the civil division was granted.