Police were not politically motivated when they said Gerry Adams should not be prosecuted for allegedly withholding information about his paedophile brother, a watchdog has found.
The Northern Ireland Police Ombudsman said there was no evidence of misconduct, or that officers had been influenced by the Sinn Fein president's status.
Dr Michael Maguire said: "The documentation we have examined shows that the police recommendation not to prosecute Mr Adams followed from an appropriate interpretation of the law as well as some concern over the precedent which such a prosecution could set.
"I have found no evidence to indicate that their thinking was influenced by who Mr Adams was."
The Ombudsman received a complaint shortly after Liam Adams was convicted and jailed in 2013 of raping and abusing his elder daughter Aine Dahlstrom.
The abuse began when Ms Dalhstrom, who has waived her right to anonymity, was just four years old and continued over a six-year period during the 1970s and 1980s.
Gerry Adams, a Louth TD, testified at his brother's first trial - which collapsed in April 2013 for legal reasons.
He told the court that in 2000, during a walk in the rain in Dundalk, his brother had admitted sexually abusing his daughter, Ms Dalhstrom.
Mr Adams made his first report to police about the allegations in 2007 shortly after his party voted to accept the PSNI, but did not tell officers about the confession until 2009, when he made a second statement.
Mr Adams did not give evidence at the second trial for technical reasons.
Last month, a review by Northern Ireland's Attorney General John Larkin QC, concluded that it was not in the public interest to prosecute the senior politician.
The Ombudsman said police had been "alive" to the issue of potential criminality - but two senior officers, a detective inspector and detective chief inspector found there was insufficient evidence to proceed.
Dr Maguire added: "It is clear that Mr Adams did not report either conversation immediately to the police. It is also clear that, at one stage, police considered whether or not this delay could be regarded as 'withholding information'."
It was also revealed during discussions with the Public Prosecution Service (PPS), police were advised that, because of the nature of the information, Mr Adams's actions did not meet the legal definition of "withholding information".
And a memo dated October 24, 2011 from the PSNI to PPS set out the potential implications for prosecuting a family member, where their evidence supports the prosecution.
Dr Maguire said: "My findings in this case arise from a very particular set of circumstances and how they applied to a particular piece of legislation. In relation to this case, I found no evidence of misconduct concerning any of the officers involved.
"Indeed, the officers were cognisant of how important it is for relatives to come forward with information which may assist in the prosecution of such allegations of historic sexual abuse."