PSNI sources have rejected claims by Sinn Féin that police this week turned away a key suspect and a key witness to the murder of Robert McCartney.
One senior police source accused republicans of engaging in a "sideshow" as Sinn Féin's chief negotiator, Martin McGuinness, said there was growing evidence that the PSNI was holding back on charging suspects in order to damage Sinn Féin.
"Police refute the distractions which have been peddled. Our sole interest is to bring to justice the killers of Robert McCartney, and give closure to the McCartney family," was the official police response to Mr McGuinness's complaints.
Police sources said the PSNI was constrained in responding to specific complaints by republicans because it must not say or do anything that could prejudice any future court cases against those allegedly implicated in the murder.
A senior republican source told The Irish Times on Monday night that a key witness, understood to be Brendan Devine, who was also stabbed and badly wounded on the night of the murder, wanted to give a statement to the police on Monday.
This would have "allowed immediate arrests and charges to be brought", said the republican source.
It is understood, however, that Mr Devine informed police that he had nothing new to add to a recent statement given to police.
The key suspect, according to the republican source, also made himself available through his solicitor to meet the PSNI, but the police did not interview him. This suspect allegedly disposed of the murder weapon and other evidence on the night.
Again it is understood that police are making arrangements to interview this suspect, but at a time when detectives judge it would be appropriate to the conduct of their investigation.
Police and McCartney family sources have repeated that despite republican protestations of support for the family and notwithstanding Mr McGuinness's comments in recent days, no testimony has so far been produced that could convict the killers.
Legal sources such as SDLP lawyer and Assembly member Alban Maginness have also stated that police must be extremely careful in how they handle the investigation.
Mr Maginness said that if witnesses came forward to give evidence on the instructions of the IRA or Sinn Féin such evidence could be rendered inadmissible.
Mr McGuinness repeated his advice to the McCartneys yesterday - which he said was not a threat or a warning - "that there are elements that are prepared to manipulate the McCartney case for political advantage".
"The PSNI is clearly involved in such manipulation. The PSNI's approach is not about justice; it is about damaging Sinn Féin."
The five McCartney sisters and Bridgeen Hagans, partner of Robert McCartney, flew to the US from Dublin yesterday morning. Before leaving, Catherine McCartney said there was no danger of the family being exploited by anyone.
"We have to be very careful that we're not being used by anybody, and that includes Sinn Féin and all political parties. We're not stupid women."
Meanwhile, relatives of Derry man James McGinley (23), who was stabbed to death in October 2003, have sought a meeting with Sinn Féin president Gerry Adams.
The family claims the man jailed for his manslaughter last month, Bart Fisher, is in the IRA, and that its members intimidated them during the trial.
