The NYPD deployed body cameras to a select group of officers Thursday as part of its trial run with the technology.

Officers at the 34th Precinct in Manhattan are the first to wear the cameras. Another 20 precincts are getting them by the end of the year.

The hope is that all 22,000 patrol officers will have cameras by the end of 2019.

Mayor Bill de Blasio and police Commissioner James O'Neill say the bodycams will promote accountability and transparency.

The devices record audio and video, and police wearing them have to follow 50 pages of guidelines.

Among the rules, officers are required to activate them on all enforcement or investigative encounters, but the cameras must be turned off during interviews with informants of victims of sex crimes.

Critics say they guidelines offer too many loopholes for police officers that could be potentially dangerous.