A 17-year-old boy is due to appear in court today charged with the murder of Constable Stephen Carroll in Co Armagh earlier this month.
The teenager, set to go before Lisburn Magistrates Court, is also charged with membership of a proscribed organisation, the dissident republican Continuity IRA, possession of a firearm with intent and collecting information likely to be of use to terrorists.
Con Carroll, 48, from Banbridge, Co Down was shot dead in Craigavon while answering a call from a woman who had a brick thrown through her window.
Four other people remain in custody being questioned about the murder as do four arrested over the murder of two soldiers in Antrim 48 hours before the policeman died.
Last night two men, aged 27 and 31, who had been questioned for a week about the murder of Con Carroll, were released without charge.
Meanwhile the High Court in Belfast is expected to rule today whether six people being questioned about the murders of Con Carroll and the two soldiers can challenge their lengthy detention by police.
They are among eight people still being held over the dissident republican murders of Con Carroll and Sappers Mark Quinsey, 23, from Birmingham and Patrick Azimkar, 21, from London who were murdered outside Massereene Barracks in Antrim.
The Real IRA claimed responsibility for murdering the soldiers who were attacked as they collected a pizza from a delivery driver at the gates of the barracks.
The Continuity IRA said they were responsible for the murder of the policeman.
The six who police have been given permission to question for a second seven-day period are seeking to challenge their extended detention.
They are the first people to be held in the North under the Terrorism Act of 2006 which means they can be held for up to 28 days.
Only one of the six being questioned about the soldiers' murders, prominent Craigavon republican Colin Duffy, was identified when the action was launched yesterday. The others were granted anonymity.
Lawyers representing the six are seeking an urgent judicial review on the basis that their extended detention is unlawful and breaches their right to liberty under the European Convention on Human Rights.
Duffy was allowed into court under police guard for the hearing.
The court is due to rule later whether the judicial review can go ahead and test the legality of their detention.
In a separate move, the Northern Ireland Human Rights Commissioner Monica McWilliams has condemned the continued detention of those still held without charge.
She visited the PSNI Serious Crime Suite at Antrim police station last night to inspect conditions under which they were being held.
She was granted permission to visit after the six launched their High Court action.
Ms McWilliams said afterwards she was worried people were being held for so long in cells designed for short stays.
"We have always been against these lengthy detention periods. The issue should be to charge people or to release them now after this length of time.
"Obviously there are serious issues at stake here, but these individuals would themselves say: 'Produce the evidence'."
She added: "Some of them have not even been interviewed for a number of days now."