Many adjourned but not concluded as families of those killed claim hearings deliberately being delayed to conceal the truth

Inquests into more than 70 killings during Northern Ireland's Troubles have still to be concluded, owing to delays that are causing anger among relatives of the dead and raising concerns about the ability of coroners courts to cope with the conflict's legacy.

The unfinished inquests stretch back decades and largely concern gunshot killings by police and troops in circumstances that are bitterly disputed, or killings by paramilitaries suspected of having links with the security forces.

The average time families have waited for a conclusion to adjourned inquests is 20 years and seven months. Many of the reopened inquests waiting to be heard concern deaths that occcurred as far back as 1971. The majority of the cases have not led to prosecutions.

Coroners and lawyers representing the families of the dead have complained about repeated failures by lawyers representing the police and Ministry of Defence to disclose documentation that would allow the inquests to be completed.

The families, who are mostly nationalists, say hearings are being delayed to conceal the truth about the killings.

Unionist politicians and retired police officers, meanwhile, say they fear the inquest system is being manipulated in the service of a new narrative of Northern Ireland's past in which killings by paramilitaries are overlooked, and the difficulties and dangers once faced by the security forces are largely forgotten.

What is not disputed is that 16 years after the Good Friday peace agreement was struck, 46 inquests into the killings of 74 people remain outstanding in Northern Ireland.

About half the inquests were opened shortly after the deaths happened but were adjourned and never concluded, while half were reopened in recent years on the orders of John Larkin QC, the attorney general of Northern Ireland, following complaints that the original hearings were fundamentally unfair.

Northern Ireland's senior coroner, John Leckey, has expressed exasperation at the length of time some inquests are taking.

Comparing the time taken to conclude some cases from the Troubles with the inquests into the 7/7 London bombings and the death of Diana, Princess of Wales, he said in February: "Looking at how difficult inquests have been held in England, I feel embarrassed."

Mark Thompson, director of Relatives for Justice, a non-governmental organisation that works with many of the families, believes police are determined that some of the key documentation about the killings should never see the light of day. "It's initially a case of deny, deny, deny, then delay, delay, delay," he said.

Last year a judge at the European court of human rights said that police and soldiers responsible for killings in Northern Ireland could "benefit from virtual impunity" because of the length of the delays.

Meanwhile, the Committee on the Administration of Justice, a Belfast-based human rights group, said: "We retain concerns about protracted delays by the security forces in disclosing information, and limitations on the inquest system itself."

In particular, the organisation said, the law that prevents inquests in Northern Ireland from recording unlawful killings and requires jury verdicts to be unanimous, needs urgent remedy. Without an unlawful killing verdict, many families hoped for forceful narrative verdicts.

The delayed inquests include the decision about the death of Roseanne Mallon, 76, shot dead in May 1994 by a Loyalist Ulster Volunteer Force gunman while she was sitting on a settee at her-sister-in-law's home in Tyrone.

The inquest began eight years after her death but was adjourned more than 20 times over the following two years as lawyers representing her family tried to discover more about two army surveillance cameras overlooking the scene.

The lawyers in this case also faced problems as they tried to get information from the MoD about six soldiers who had been hiding nearby and who said they were ordered not to react to the shooting. The inquest was reopened again last year, then adjourned until next month, the 20th anniversary of her death.

Six of the delayed inquests concern the deaths in 1982 of Republican paramilitaries allegedly shot dead when they could have been arrested.

The deaths are said to have happened owing to the "shoot-to-kill" policy that was later investigated by John Stalker, deputy chief constable of Greater Manchester. His report (completed after he was removed from the inquiry in controversial circumstances) has never been made public, and the reluctance of government lawyers to disclose it to the dead men's solicitors is said to have added to delays.

The reopened inquests include five that will examine the shooting dead of 10 people in Ballymurphy, west Belfast, during two days of disturbances triggered by the introduction of internment without trial in August 1971. One of those who died was a priest shot while giving the last rites to a young man; another was a 50-year-old mother of eight, shot in the face from a distance of about 200 metres.

Five months later, on Bloody Sunday,, soldiers from the same unit, the 1st Battalion, the Parachute Regiment, shot dead 13 people and wounded 13 others, one fatally, in Derry.

Another reopened inquest is to look again at the deaths of 10 Protestant workmen who were lined up against their van and mown down by gunmen in January 1976. The killings were claimed by a group calling itself the South Armagh Republican Action Force; a renewed police inquiry concluded in 2011 the IRA was responsible.

This month, at one Belfast coroner's court, a series of opened and adjourned hearings briefly touched upon, but did not illuminate, some of the tragic deaths of the Troubles.

Court staff said the schedule was entirely typical. Monday morning began with a brief hearing in the case of Francis Rowntree, 11, who died in April 1972 after being shot in the head by a rubber bullet fired at close range by a soldier.

This case was followed by brief proceedings about Manus Deery, 15, who died in Derry in May 1972, hit by fragments of a bullet fired by an army sniper. He was carrying home his family's fish-and-chip supper.

Next came a brief hearing in the case of a man shot by soldiers during a fracas in a Belfast dance hall in December 1971.

As with other cases, lawyers for the Police Service of Northern Ireland (PSNI) told the court that officers were busy dealing with other historical cases, and it was unclear when they might find time to locate and disclose files on the killing.

Later that week there was a brief hearing in the case of a teenage member of the IRA who bled to death after being shot in disputed circumstances in Derry in July 1972.

This was followed by a hearing – quickly adjourned – into the deaths of four members of the IRA shot dead by the SAS in County Tyrone in January 1992. Their families' lawyers allege that the way in which they were ambushed amounted to a breach of their right to life under Article 2 of the European convention on human rights.

Further proceedings concerning the 10 Ballymurphy deaths and an Irish National Liberation Army killing from 2004 that had been due to be brought before the court that week, were adjourned without hearings.

While coroners courts in England and Wales conduct hearings that are essentially inquisitorial, some of the proceedings at the Belfast court had an adversarial air about them. In between hearings, lawyers were heard chatting about other inquests: "Ah, that one's been adjourned for another year."

Meanwhile, disquiet about the way in which the inquest system is operating in Northern Ireland is growing.

This year, a case at Belfast's high court that heard a litany of complaints about the inquest of an IRA member led to a judgment that could have huge implications for the coroner's courts system in Northern Ireland.

After a judicial review of the inquest into the death of Pearse Jordan, who was shot in the back by police in 1992, Mr Justice Stephens found police had "created obstacles and difficulties" that led to the inquest being delayed up to 11 years and had redacted documents so heavily they were left unintelligible.

The judge also said that lawyers for the dead man's family should not have been denied access to the Stalker report, and that coroners should not sit with juries when there is a risk of bias. The coroner and chief constable are appealing against this ruling.

Asked about the views that delays in disclosure of relevant material was causing inquests to drag on for decades, the MoD had no comment.

The PSNI said: "The PSNI is working closely with the coronial service to try to progress these legacy inquests." It would say nothing further.

In a post-conflict society that remains deeply divided, and in which there is little agreement on what happened during the Troubles or why, many unionists say they are uneasy at the prospect of inquests being turned into mini public inquiries at which former soldiers and retired police can be compelled to give evidence, but former paramilitaries cannot.

The Ulster Unionists' position paper on dealing with the past warns that historical inquests "run the risk of establishing a narrative of actions by security force personnel, without a reciprocal narrative concerning terrorist motivation and activity, or any due attention to the security and political context of the time".

The PSNI has been holding "information evenings" to give retired officers advice on giving evidence at inquests.

There is no agreement about how Northern Ireland can confront its past, or even the language that should be used to describe it.

The former Northern Ireland secretary Peter Hain suggested last week that it was time amnesties were granted to all those who had committed terrorist crimes, but the idea was dismissed by David Cameron and the Irish president, Michael D Higgins, who made the first state visit to Britain by an Irish head of state. He said: "There are a lot of very difficult memories and it would be, to my mind, wrong to suggest to anyone that you should, as it were, wipe the slate clean."