Police

Like Alycia, I had trouble finding a single source on police dissent. Below, I have a bunch of articles and some academic texts that I hope are helpful.

In addition to the examples that Alycia provided, there’s also a famous and recent incident with a retired Philadelphia police chief Ray Lewis protesting at OWS:
http://philadelphia.cbslocal.com/2011/12/08/retired-philly-police-captain-arrested-in-ny-occupy-wall-street-rally-warned/

This is an article that interviews Lewis, and documents one other Oakland police officer on the record as supporting OWS:
http://rt.com/news/police-join-protesters-ows-621/

These were the only references I could find to police joining OWS protests, but I thought I’d also point you to an article about Michael Moore calling for police to join OWS
http://newsbusters.org/blogs/noel-sheppard/2011/10/15/michael-moore-calls-police-join-occupy-wall-street-protests-egyptian

In terms of what I could find about police and protesting, there are two main strains - whiste blowing on police corruption and protesting against working conditions.
About the former, this is a legal article on what makes whistle blowing difficult in police culture and why it’s necessary:
http://www.bmartin.cc/dissent/documents/Johnson.pdf
Here’s another academic article on obstacles to whistle blowing among police:
http://cad.sagepub.com/content/53/4/605.abstract

And here are some news articles on different instances of whistle blowing in various police departments:
http://blog.oregonlive.com/oregonianextra/2008/05/whistleblowing_lawsuit_former.html
http://www.baconalert.com/2011/07/13/newark-police-officer-allegedly-fired-for-whistle-blowing-on-corrupt-cops-newark-new-jersey/

I could not find any definitive answers, but the following articles offer some context on how the term might have started.

An essay called "The Endless Dream Game of Death", by Luis Rodriguez states that the LAPD began using the term during the 1980's, to dismiss victims of gang violence.

In "NHI-No Humans Involved," UCSD faculty member Elizabeth Sisco, traces the use of the term to the San Diego area during the 1980's and 1990's, by San Diego police, to address a series of murders and sexual assaults against women. Sisco wrote that the head of the task force assigned to investigate the murders claimed that the use of "NHI" is fictionalized by old detective novels, but another San Diego officer confirmed the use of the "NHI" term in a Sacramento Bee article to describe these murders.

Rodriguez, Luis J. and D. Cesare (1995). Endless Dream Game of Death. Grand Street, No. 52, Games. pp. 61-77. http://www.jstor.org/stable/25007852. Access December 6, 2009 from Jstor database through San Jose State University.

Sisco, Elizabeth. (1993) NHI-No Humans Involved. NHI-No Humans Involved. Accessed December 6, 2009.