From an interview with filmmaker Nick Broomfield on his documentary, Tales of the Grim Sleeper:
NB: There is a police slang term that, when the police call in a homicide, for example, they would say ďNHI,Ē [meaning] ďno human involved.Ē Which [means] donít really bother with proper forensics. Heís a John Doe or Jane Doe. Itís a homeless person, a drug addict, prostitute, gang member, we donít really care. We probably donít expect to find the person responsible. Just book it in. But donít spend a lot of time on it.
Thatís kind of what it means. Itís used for disposable people. People who arenít worthy of a proper inquiry. And again, disposable people, people who obviously arenít represented, arenít considered part of the political process, have no employment. They donít count.