Police gang expert Alex Rollin was among four officers who were promoted by the Bermuda Police Service this week.Mr Rollin, along with Derek Berry, were promoted from Sergeant to Inspector and Krishna Singh and Mark Monk moved up from Constable to Sergeant.All four were promoted by Commissioner of Police Stephen Corbishley in a ceremony with Wayne Caines, the Minister of National Security, and friends, family and colleagues on Monday.Inspector Rollin completed his recruit foundation course in 1999 and served in St George’s and in the Police Support Unit before he became a Sergeant in 2004.He became a key figure in gang-related trials in the Supreme Court and has given evidence in about 35 court cases. Inspector Rollin has also made presentations on gangs in schools and government departments and had delivered lectures to the Jamaica Constabulary Force on gang evidence.Inspector Berry became a police officer in the UK in 1990 and worked with Northumbria Police in the North East of England for ten years.He joined the Bermuda service in 2000 and now has a lead role in the Critical Incident Stress Management Team which he has been a member of, off and on, since it was set up about 17 years ago. Sergeant Singh joined the Bermuda police in 1996 and has worked as a patrol officer and assisted the criminal investigation unit and police support unit.He has served as Southampton Parish Constable in his most recent role.Sergeant Monk joined the BPS in 2004 and worked in operational policing before he was transferred to Somerset Police Station.He was recently awarded a Commissioner’s Commendation for his work on a new 12-hour shift system.