Notorious police killers in prison
A notorious police killer is to be released from prison after more than 45 years.
Harry Roberts, 78, was jailed for life for murdering three unarmed officers in Shepherd's Bush, west London, in 1966.
But a number of other police killers are still serving their sentences in jail.
The former US marine was jailed for life for the murder of PC Ian Broadhurst, who was shot in Leeds on Boxing Day 2003.
Bieber shot PC Broadhurst in the head at point blank range despite the 34-year-old pleading for his life.
He was also convicted of the attempted murders of PCs Neil Roper and James Banks.
Cregan was jailed for four murders, including those of two police officers in Greater Manchester.
He admitted killing PCs Fiona Bone and Nicola Hughes in a gun and grenade attack and father and son David and Mark Short.
He also admitted the attempted murders of John Collins, Michael Belcher and Ryan Priding during the attack on Mark Short at a Droylsden pub in May 2012.
PC Sharon Beshenivsky, 38, was killed outside a travel agency in Bradford, in November 2005.
Jama, 29, who denied murder, was convicted after a retrial at Newcastle Crown Court.
He was part of a gang that shot the popular officer and wounded her colleague PC Teresa Milburn as they responded to an alarm call at the business.
The gang believed that up to £100,000 could be inside, but they escaped with little more than £5,000.
Ikechukwu Tennyson Obih
Obih, 29, stabbed Bedfordshire PC Jon Henry twice in the chest as he tried to arrest him in Luton town centre in 2007.
He was convicted of murder despite claiming manslaughter on the grounds of diminished responsibility.
The 36-year-old policeman was one of four officers called to George Street after window cleaner Stephen Chamberlain was stabbed.
Obih was found guilty of attempting to murder Mr Chamberlain.
Bourgass murdered Det Con Stephen Oake in 2003.
Bourgass had gone on the run after police discovered what was a plot to manufacture and spread ricin and other poisons on the UK's streets.
Police launched a nationwide search to find Bourgass, who fled from London to Manchester, where he was captured in January 2003.
It was there, during a desperate bid to get away, that he stabbed Det Con Oake to death with a kitchen knife and injured four other officers.
Nelson murdered a policeman and bouncer in south London in 1993.
Unarmed PC Patrick Dunne was shot in the chest as he went to investigate the sound of gunshots at doorman William Danso's home.
In 2006, he was told he must serve at least 35 years in jail.