A 37-year-old man has been charged with the murder of Constable Stephen Carroll earlier this month and possessing a firearm with intent to endanger life.
He is expected to appear in court tomorrow morning.
Details of the court have yet to be confirmed.
Constable Carroll was shot dead in Craigavon, Co Armagh, on 9 March.
Earlier, a 17-year-old was remanded in custody charged with the murder of the PSNI officer.
The youth appeared at Lisburn Magistrates Court this morning.
The accused is also facing charges, including membership of the Continuity IRA, a proscribed organisation.
He will appear by a videolink at a court in Craigavon on 3 April.
Detectives investigating Constable Carroll's killing and the murders of two British soldiers in Antrim on 7 March have a total of seven other people in custody.
Six of those detained have challenged the extension of their detention period.
After hearing submissions from both sides, Northern Ireland's Lord Chief Justice, sitting with two other judges, reserved judgment until the morning.
All six claimed a decision to detain them for an extra seven days, while police awaited the result of forensic tests, was unlawful and breached their right to liberty under the European Convention on Human Rights.
Yesterday, Northern Ireland's Human Rights Commissioner Monica McWilliams said she is concerned about the length of time detainees have been held without charge.
Under the Terrorism Act of 2006, suspects can be detained for up to 28 days.
But in Northern Ireland the controversial provision has never been used for the full 28-day period.
