In most murder investigations finding the murder weapon would be regarded as a major step towards finding the killers.
But the investigation into the murder of Belfast solicitor Pat Finucane in 1989 was different in many ways.
Finding the murder weapon in this case was, it seems, inconvenient. At some stage someone within what was then the RUC decided that the Browning pistol should be returned to the British Army from where it had been stolen by loyalists.
RTÉ's Richard Dowling blogs about the legal argument and impediments he faced in the investigation into the murder of Pat Finucane
Conveniently that destroyed any evidential value the weapon might have had.
It is clear why this was done. Some members of the RUC Special Branch and the British Army's agent handling outfit, the Force Research Unit, had a good idea who the killers were.
Mainly because it seems they had helped them target Finucane.
He was shot him dead as he and his family had Sunday dinner. Some RUC and military intelligence officers knew who the killers were but didn't pass it on to those actually investigating the murder.
Using agents and informers is a very precarious task for law enforcement organisations worldwide.
Those agents with the best information are those closest to the action. That, by its very nature, means they're involved in law breaking. It is understandable why police and intelligence organisations would seek out such people - to give them a better understanding of what is going on.
But the Finucane case goes way beyond that. It involves the deliberate targeting of a solicitor by officers whose job it was to uphold the law. In effect, they used loyalist gunmen to assassinate Finucane.
Some officers believed he was working for the IRA but his family always denied that and nothing has emerged to prove it. This and other similar cases give rise to concerns that what went on during the 'Dirty War' in the North was more akin to the activities of a South American junta than a western democracy.
When John Stevens investigated the murder of Pat Finucane in the 1990s he experienced strenuous efforts by persons unknown trying to prevent him discovering the level of collusion.
Agents in loyalist gangs were tipped off before they were due to be arrested and the Stevens' team offices inside a secure RUC barracks were set on fire. The phone lines and fire alarms didn't work. Coincidence? He didn't think so.
Despite years of work only four short chapters were ever published summarising his findings in a report known as Stevens III. He found there was collusion between the security forces and loyalist killers in the murder of Pat Finucane and the murder of a Protestant youth, Brian Adam Lambert, who was killed by loyalists in the mistaken believe he was a Catholic.
But the vast bulk of what Stevens found out has never been made public. In an effort to redress that I submitted a request under the UK Freedom of Information Act to the Police Service of Northern Ireland seeking a copy of Stevens III.
It is worth nothing that I still can't do that here as the Garda Siochana are still outside the remit of FOI in Ireland.
Tortuous legal argument
It has taken me four years of tortuous legal argument with the PSNI, the UK Information Commissioner and a Tribunal to get more details about Stevens III.
The request under the UK Freedom of Information Act seeking a full copy of Stevens III (with the necessary redactions to protect sources) was refused by the PSNI. I then appealed to the UK Information Commissioner. My appeal was rejected there after the Commissioner's office discussed the matter with the PSNI but without having ever having seen any part of Stevens III. Then I appealed it to the First Tier Tribunal where the argument was basically did Stevens III 'relate to' the security services. While the work of MI5 is exempt from FOI, the work of the police – even the Special Branch – is not.
Eventually the Tribunal decided that while much of Stevens III was exempt, some of it could be released – mainly Chapter 6. Only four chapters were ever published before so it is clear there is still a hidden Chapter 5 still and possible other chapters 7, 8, 9 etc.
The appeal to the Tribunal was argued in papers and written submissions to keep the costs down. While for RTÉ it involved just me doing my own research, for the PSNI it involved legal counsel at unknown cost. And for what?
There is nothing in Chapter 6 of Stevens that threatened the national security of the UK. There is nothing there than could not have been released when Stevens was originally published in 2003. It could and indeed should have been published a long time ago.
What there is in Chapter 6 is damning information about the RUC conduct of the Finucane murder investigation and the willful destruction of evidence.
There is also evidence of rather pointless editing to try and limit the 'damage' to the RUC's reputation - for example removing the phrase "of nationalists" from a sentence in the introduction where Stevens talks about murdering of civilians.
The Finucane family are maintaining their demand for a full public inquiry. The British Government originally promised it would happen along with a number of others (like the inquiry into Rosemary Nelson's death and the Smithwick Tribunal which is still running here).
However, it seems the British Government has backed away from a public inquiry. The probable reason is to try and avoid exposing the security forces' involvement in 'Dirty War' as much as possible.
Instead the Government of David Cameron asked a respected lawyer, Desmond de Silva to re-examine the circumstances surrounding the murder of Pat Finucane – a move criticised by the family as inadequate.
His report is due to the published on Wednesday. Will we find out more then about the murder of Mr Finucane? Probably. Will we find out everything? Certainly not.
What happens after Wednesday largely depends on the British and, to a lesser degree, the Irish Government and their desire to uncover the truth.