Gerry Adams arrest leaves Sinn Féin/PSNI relations strained
Sinn Féin's endorsement of the Police Service of Northern Ireland (PSNI) was one of the most significant elements of the peace process.
For generations, republicans viewed the police as enemies, as the guardians of what they said was an artificial state.
When the party joined the Policing Board - the oversight body that holds the PSNI to account - in May 2007, it was hailed as a move of historic significance.
Since then Sinn Féin has repeatedly stated its support for the police, encouraged young Catholics to join, and criticised dissident republicans who murdered two officers, Stephen Carroll and Ronan Kerr.
Its response to the arrest of Gerry Adams last week has raised questions about the extent of that support.
At a press conference on Friday, Deputy First Minister Martin McGuinness issued what was viewed as a threat, that the party could reconsider its support for the PSNI if Gerry Adams was charged in connection with the murder of mother of 10 Jean McConville. It is an allegation the Sinn Féin leader has strenuously denied.'Dark side'
Mr McGuinness said a decision by the police to seek an additional 48 hours to question Mr Adams, which they were granted by a judge, confirmed his view that the timing and arrest had been politically motivated.
He spoke of a "dark side" within the police who he said were opposed to the party. It is not a new phrase. Sinn Féin has been making the accusation for the past three years.
Mr McGuinness went further, claiming there was "a cabal within the PSNI" who were pursuing "a negative and destructive agenda to both the peace process and to Sinn Féin".
Shortly after his release from police custody on Sunday night, Mr Adams said he wanted to make it clear that he supported the PSNI.
But he criticised the decision to arrest and question him, describing it as "the old guard using old methods", and those involved as "enemies of the peace process".
The term "old guard" is a reference to some of those within the PSNI who were previously members of its predecessor, the Royal Ulster Constabulary (RUC).
The extent of republican hostility towards the RUC is demonstrated by the fact that they killed more than 300 of its officers during the Troubles.
Those are strong words that cannot be retracted.'Legitimate and lawful'
The allegations have been rejected by the chief constable of the PSNI.
On Tuesday, Matt Baggott said that questioning the motivation or impartiality of the police was "unfair and inappropriate".
In a statement, he said the accusation of a dark side within the PSNI was one he refuted.
He said the arrest and questioning of Mr Adams was legitimate and lawful, and that an independent judge subsequently decided that there were grounds for further detention.
The chief constable said it would have been wrong to treat the Sinn Féin leader any differently to other citizens.
"In a democracy the police are tasked with following the evidence without fear or favour and in accordance with the law. The PSNI are committed to doing so regardless of any undue pressures," he added.
So what damage has this done to what has often been an uneasy relationship between Sinn Féin and the PSNI?
The party has made it clear that its support is qualified. It supports what it calls "progressive elements" within the police service, but opposes small number of officers it refers to as "the old guard".
The police strongly reject the suggestion that any such "cabal" exists, and insist the arrest of Mr Adams was a logical step by detectives investigating the murder of Jean McConville.No prospect of divorce
There is no prospect that the two sides will make up and reach an agreed position on the decision to arrest the Sinn Féin leader.
However, there is also no prospect of a divorce. Sinn Féin is not going to leave the Policing Board or withdraw its support for the PSNI.
The relationship will continue, but could be very fractious in the weeks ahead.