The family of one of the victims of the IRA bomb attacks in Birmingham have called for the authorities to re-investigate the case.
Campaigner Julie Hambleton said police should do "what they are employed and paid to do" as the 39th anniversary of the pub bombings approaches.
A total of 21 people were killed and 182 injured on the night of November 21 1974, when the Provisional IRA bombed the Mulberry Bush and the Tavern In The Town.
West Midlands Police said its counter terrorism unit has spent the past 18 months assessing and cataloguing more than 10,000 documents and exhibits to see whether a new inquiry is viable.
Prime Minister David Cameron has also been handed a report compiled by campaigners.
Ms Hambleton, whose sister Maxine was 18 when she was killed in the attacks, told BBC News: "It's a nightmare, you live with the grief and loss every single day of your life. We've lived our lives because Maxine would have wanted us to do that but justice for the 21 is fighting for those who aren't here to fight for it themselves."
Six men were jailed over the atrocity but had their convictions quashed in 1991 when the Court of Appeal ruled that the forensic evidence that helped convict them was unsafe.
Ms Hambleton met with one of the men, Paddy Hill, for a BBC documentary and said it w as "awful" to come face to face with someone she had previously thought responsible for her sister's murder.
But she added: "He understood that and he fully supports our campaign. Our battle now is with the authorities and the Government to recognise the fact that the perpetrators still have their liberty and no one is looking for them."
Hill was one of the men who became known as the Birmingham Six who had false confessions beaten out of them by British police following the horrific terror attacks.
Along with Hugh Callaghan, Billy Power, Johnny Walker, Richard McIlkenny and Gerry Hunter, he was sentenced to life with no release date on the basis of the admissions before being freed 16 years later.
Nobody has ever been brought to justice.
Assistant Chief Constable Marcus Beale said: "We don't underestimate the impact this continues to have on victims and their families. But it has long been our position that we would reopen the investigation if significant new lines of enquiry came to light.
"The work we have been doing over the past 18 months will put us in the best position possible to be able to assess the importance and context of any information that we receive.
"With the events having taken place nearly 40 years ago, and with so much material being held in a variety of different places, it was important for our corporate understanding of the pub bombings to have all the material brought together, assessed and stored to current-day standards.
"This has been a major undertaking with over 10,000 separate documents or items identified so far. We aim to complete the task by spring next year.
"We have also asked two leading independent scientists - one in Britain and one in the Netherlands - to assess whether any new forensic opportunities might exist. This work is ongoing."
BBC1 Midlands' Inside Out programme is on Monday at 7.30pm.