For more than 20 years New South Wales Police have marched in the Sydney Gay and Lesbian Mardi Gras. 

But not this year, with the board of the event telling them to stay away. 

It comes on a difficult week for the force after a senior constable was charged with the alleged murder of Sydney couple Jesse Baird and Luke Davies. 

But police participation in the event has long caused controversy. Today we unpack why. 

Featured: 

Nicole Asquith, the professor of policing at the University of Tasmania and the convenor of the Australian Hate Crime network