The 10 people arrested by police about the murder of a Belfast man have stayed silent under police questioning, a senior detective has said.
Relatives of Mr McCartney give their reaction to Sinn Fein action
Robert McCartney, 33, was murdered on 30 January after a row in a bar. His family claim republicans were involved in the killing and subsequent cover-up.
Earlier Sinn Fein said it had suspended seven party members.
DS George Hamilton said "suspensions and expulsions from political parties are insufficient" for the PSNI.
"What we need is for people to feel free, to feel comfortable to provide evidence to the police service so that we can bring those responsible for this brutal murder to justice so that due process can take place and people can be brought before the courts," he said.
"Of the 10 people that have been arrested, they have exercised their legal right to remain silent and not to engage with us during the interview process."
He said anyone with information could approach the police ombudsman if they did not wish to speak with the PSNI.
Sinn Fein President Gerry Adams said the family handed him a list of people they alleged were involved in the murder at a meeting last month.
He said seven of those on the list were Sinn Fein members and they had been suspended without prejudice and told "to provide full and frank statements".
The party has also instructed a solicitor to pass on the names to the ombudsman.
The McCartney family said the suspensions were "a belated step forward".
"The basic action taken by Sinn Fein in relation to their members involved in Robert's murder is nothing more than what would have been expected from any democratically elected party.
"Although we would have liked this to have happened earlier as those names have been known to Sinn Fein officials from the outset.
"The handing over of the names to the police ombudsman through a solicitor is of symbolic significance.
"Providing a solicitor with a statement to be passed on to the ombudsman is an inadequate method of gathering evidence." The McCartney family said they intended to travel to Washington for St Patrick's week.
The suspensions come a week after the IRA said it had expelled three of its members over the Short Strand man's killing.
Police Ombudsman Nuala O'Loan said eye-witness statements to her investigators could be used in the trial of anyone charged with the murder.
"We can offer something which priests and solicitors, who are the other people who have been suggested to take this evidence, can't offer," she said.
BBC Northern Ireland security editor Brian Rowan said he understood that there "is no overlap between the three IRA members who were expelled and now the seven Sinn Fein members who have been suspended from the party".
He added: "It is my understanding that it is one of the three IRA members expelled a week ago who is the main suspect in the McCartney murder."