Niven has over 30 years experience as a police officer, having first joined Strathclyde Police in 1985 and gained his initial police experience in Ayrshire where he became a Detective Officer.  He transferred to Glasgow on promotion to Sergeant in 1992 before returning to Ayrshire as an Inspector, Chief Inspector and Superintendent. In 2009 he was appointed Head of Road Policing for Strathclyde Police before becoming Deputy Divisional Commander in Renfrewshire and Inverclyde. 

Niven was heavily involved in the Scottish police reform process and represented the Association of Scottish Police Superintendents throughout the implementation of Police Scotland in 2013. In 2014, he became a Chief Superintendent and President of the Superintendents Association. This high profile position required him to become the public face of the operational leaders of the police service in Scotland, appearing regularly on television and widely quoted in our newspapers.  As Chair of the staff side of the Scottish Police Negotiating Board, Niven led pay negotiations for all police officers in Scotland. 

Following retirement from the police in 2016, Niven became the Chief Executive Officer of South Ayrshire Escape from Homelessness (SeAscape), a charity offering support to those in poverty or housing need in the Ayrshire area.

In July 2018, Niven was appointed as Director of the Scottish Violence Reduction Unit and is now responsible for the strategic direction of the Unit and represents the initiative on a number of national bodies.