Gerry 'The Monk' Hutch may never face fresh charges in connection with the Regency murder of David Byrne, senior sources believe.
But other arrests following the 2016 gangland killing are imminent.
Hutch, 60, walked free from the Special Criminal Court on Monday after he was acquitted of murdering the 34-year-old Kinahan cartel lieutenant.
Now a number of senior gardai are said to be concerned that Hutch faced a murder charge only - and not firearms.
One told the Irish Mirror: "He should have faced firearms charges at least. There was enough on those tapes in the jeep to bring a charge."
Gardai from the Dublin Metropolitan Region are continuing with the probe into Hutch over allegations he directed an organised crime gang.
Last night senior security sources said the possibility of Hutch facing fresh charges was slim.
One explained: "A decision was taken to charge Hutch with the murder of Byrne. And not anything else. And it backfired. And unless there is an arsenal of new evidence, the case against Hutch is dead in the water.
"If new evidence comes to light, then fair enough. But a decision was made to bring the murder charge only.
"The issue is Jonathan Dowdall appeared to be front and centre after charges were preferred.
"If there was no Dowdall, how was Hutch ever going to be convicted?
The Special Criminal Court found there was no evidence that Hutch was one of the shooters at the Regency in Feb 2016 - and he walked free on Monday.
The State's case was that Hutch of one the the gunmen in the hit squad dressed in fake Garda ERU uniforms armed with AK47s.
But the three-judge non-jury court found that Jonathan Dowdall, 44, who had turned supergrass against his onetime pal, Hutch, 'acted out of self interest' and the court was 'not prepared to act on his statement alone'.
Sources said new charges are unlikely.
One said: "He could claim he couldn't get a fair trial - because of everything that has come out in this trial - and all the exposure in the media.
"Plus with Hutch about to head off again, gardai would have to apply to whatever foreign country he is in to extradite him back.
"Can you imagine having to ask the Spanish again? They'd probably tell the guards where to go. The Spanish went all out before to get him and sent him back.
"No, unless a load of new evidence shows up, Gerry is a free man. He just has to watch out for the Kinahans, though.
"The only good thing is the Kinahan gang has been decimated by the gardai here, with most of the Irish-based gang behind bars.
"But Gerry will have to keep looking over his shoulder abroad."
Jonathan Dowdall was heard discussing the murder with the Monk on a trip north in a jeep secretly bugged by gardai.
Dowdall was due to stand trial last October charged with David Byrne's murder. His father Patrick Dowdall was charged with facilitating the murder.
But Dowdall pleaded guilty to a lesser charge and the murder charge against him was dropped. The DPP accepted a plea to the same charge as his father and Dowdall sensationally turned State's evidence against the Monk.
The State was adamant that no deal had been made with Dowdall and that his acceptance into the Witness Protection Programme was not dependent on him giving evidence.
Dowdall was given a four-year sentence and his father Patrick got two years.
Former Sinn Fein councillor Dowdall then went on to give evidence against the Monk.
But the judgement, delivered by Ms Justice Tara Burns, sitting with judges Sarah Berkeley and Grainne Malone, described Dowdall's "this pattern of lying".
Towards the end of her judgement, Ms Justice Burns said: "One wonders what the prosecution case was to be before the introduction of Jonathan Dowdall."
Over seven years on from the attack at the Regency, no one one has been convicted of the actual murder of Byrne.
One source said: "Even the court found that Gerry possession of the three AK47s. had He was on tape admitting to it. Why wasn't that on the international arrest warrant too along with the murder charge. It should have been.
"And then introducing Dowdall as a State witness just before the trial was to start was very surprising, to say the least.
"Convicting Hutch of murder hung on the court, believing Dowdall. There was no admission, no hard evidence, no CCTV - and the case crumbled.
"Dowdall was a big gamble. And it failed spectacularly."
Another source said: "Gerry Hutch is out now to live his life again."
Garda HQ would only say it 'noted' the verdict after Hutch walked. The DPP's office has not issued any statement.
Two lifelong friends of the Hutch family, Paul Murphy, 61, from Cherry Ave, Swords,Dublin and Jason Bonney, 52, of Drumnigh Wood, Portmarnock, Dublin, were found guilty on Monday of acting as getaway drivers during the Regency attack.
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