Question: The murders of which police officers led to Dale Cregan being sentenced to life in prison?
Sentence (from "Murders of Nicola Hughes and Fiona Bone"): On 18 September 2012, Police Constables Nicola Hughes and Fiona Bone, two Greater Manchester Police officers, were killed by Dale Cregan in a gun and grenade ambush while responding to a report of a burglary in Greater Manchester, England.
Relevant evidence: Yes