The daughter of Jean McConville has said she has instructed her solicitors to take a civil legal action against Gerry Adams over the abduction, murder and secret burial of her mother.
Mother-of-10, Ms McConville was dragged from her Divis flats homes in 1972 by the IRA. She was interrogated before being shot and buried.
She became one of the Disappeared and the 37-year-old's remains were found on a beach in Co Louth in 2003.
Yesterday the Public Prosecution Service (PPS) said there was "insufficient evidence" to consider a criminal legal action against Sinn Fein president Gerry Adams, the party's northern chairman Bobby Storey and five others.
Mr Adams has always denied any involvement in the killing.
Following the announcement the family said they would continue their fight for justice.
Ms McConville's daughter said she was left to take a civil legal action herself as a last resort to get to the truth.
She told the Belfast Telegraph: "For the sake of myself, my children and my grandchildren, I just want to get to the bottom of what happened to my mother.
"We waited 31 years to get my mother's body. We can't wait that long for the truth and justice - I'll not be about for that.
"There are people who know what happened, but they won't speak.
"To this day I believe Gerry Adams knows what happened to my mother.
"I can't fault the PPS and the PSNI, they can only do so much. But when people don't speak and witnesses don't come forward I am left with taking legal action myself.
"So far there has only been one man in court over my mother's murder and I am not happy with that."
The 58-year-old added: "There were a lot of lies surrounding the murder of my mother and that all needs to be cleared up for the sake of my family, we are all getting on in years.
"I can only hope this legal action will get us some justice, I feel it is the only option left to us."
Sinn Fein has been asked for a response.
Mr Adams was arrested in relation to the case last May and interviewed for four days by police.
The 66-year-old has always denied any wrongdoing.
On his release from police custody, Mr Adams said there was a "sustained, malicious, untruthful campaign" over his alleged involvement in the murder.
Adams said the PPS decision was long overdue.
“There was never any real basis for questioning me in respect of this case,” he said after Wednesday’s announcement.
“I played no act or part in Jean McConville’s death.
"I support the PSNI. But the timing of my arrest showed there remain elements within the PSNI who are against Sinn Fein. But they will not succeed.”
Last November Sinn Fein chairman and former IRA prison leader Mr Storey was arrested for questioning.
Adams and Storey were both detained on the basis of recordings from the Boston College project.
So far one person has been charged in connection with Mrs McConville's death.
Ivor Bell (78), a leader in the Provisional IRA in the 1970s, is to be prosecuted for soliciting her murder.