In the UK, Operation Griffin was underway and focusing intently on some of the most active gang members.
Meanwhile investigators in the US continued with Operation Crash which had been launched to crack down on the illegal trade in rhino horns.
Another arrest was made in the US when Michael Slattery was arrested in September at Newark airport over his part in a plot to illegally buy and sell rhinoceros artefacts in Texas in 2010.
The son of one of Rathkeale's best known traders Michael 'Laben' Slattery, he was well-accustomed to travelling back and forth across the Atlantic on business.
He certainly didn't enjoy his three months in custody ahead of his trial, complaining in court about the conditions at the Metropolitan Detention Centre in Brooklyn where he was detained.
An outbreak of disease at the lock-up meant that Slattery ended up in solitary as prisoners were quarantined.
"I nearly went insane inside the room, I'm not a bad person," he said in court.
At another hearing he said he was worried about being sexually assaulted.
Slattery said an inmate threatened to "spin my head off" after he accidentally bumped into him.
A distraught Slattery added that two other inmates, one an accused killer, argued over who would be his cellmate. The murderer "wanted me to sleep with him," he said.
"There's no way I'm staying with the fella who said he's a murderer."
Judge John Gleeson commented that Slattery looked "like a nervous wreck" but told him not worry, that the most he could get would be five years and he would still be a young man.
Slattery, a cousin of Richard O'Brien Jnr who was jailed in Colorado, pleaded guilty to the charges.
The court heard that Slattery had travelled to Texas in 2010 to buy antique rhino horn mounts. Because they were not residents, they hired a homeless man to make the purchase for $18,000 in cash before travelling to New York, where the horn was sold for $80,000.
Prosecutors said that the horns were then resold for $108,000 before being shipped out of the country to a buyer in Vietnam. His lawyers filed letters of support from a Limerick priest and a retired garda who dealt with the family in the past.
There was also a character reference from Lord Vincent Constantine who lives in Cambridgeshire. He wrote to the court about how he had known the Slattery family for years and found the then 25-year-old Michael Slattery Jnr to be "a trustworthy and courteous young man".
He added he was "extremely surprised to learn that he had been arrested and can only think his actions were taken out of stupidity and ignorance as they are totally out of character."
Judge Gleeson took a different view, saying in court: "He is no naive kid. He came here from another country to buy, in Texas, this rhino mount."
The judge's remarks came after several letters from conservation supporters had asked for the maximum sentence to be imposed.
Judge Gleeson ordered he serve 14 months, imposed a $10,000 fine, and ordered that $50,000 seized be forfeited to the authorities.
At that stage it was alleged that two other men were with Michael Slattery Jnr in Texas, his brother John Slattery and Patrick Sheridan, both of whom would later be charged and convicted by US authorities who went to great lengths to bring them to court.
In the UK police officers running Operation Griffin moved in after months of surveillance and evidence gathering.
In a series of raids in September 2013, 19 people were arrested. Both the complexity of the police investigation and the almost laughable amateurism of the Dead Zoo Gang would later be revealed in court.
Those arrested included Richard O'Brien Snr and his son Richard Jnr, although Richard Snr did not eventually face any prosecution.
Whether it was the pressure from the authorities or whether rhino horns had become harder to find, the activities of the Dead Zoo Gang came to a standstill with no more thefts being reported anywhere.
The only exception was a final smash and grab, this time at the 18th century Co Cork country mansion of Lord of the Dance star Michael Flatley.
In January 2014, thieves broke into Castlehyde where they made their way to the mansion's safari room and immediately cut away the horns of a rhino mount.
Disturbed by the burglars, the dancer and former boxing champion gave chase as the thieves ran across the lawns to a waiting car to make good their escape.
For a long time that burglary seemed to have been the last sting in the tail from the Dead Zoo Gang.
The Americans also kept after the targets they had in their sights.
Patrick Sheridan, who had accompanied Michael Slattery Jnr to Texas was arrested in 2015 as he came off a ferry from Holyhead.
In September that year he was extradited to the US. He pleaded guilty in Waco, Texas in November, and was sentenced in January 2016 to 12 months in prison and fined $1,000.
Later in the year the criminal trials as a result of Operation Griffin came to an end. Because there had been two separate trials for 14 defendants, reporting restrictions were in place until all proceedings were finished.
There was little wriggle room for Richard 'Kerry' O'Brien Snr's family, which was described as having been "at the heart" of the conspiracy to steal priceless museum exhibits and rhino horns.
In April it emerged two of O'Brien's sons, his brother and a nephew were among the men jailed for the conspiracy to steal Stg£71 million worth of museum artefacts.
His sons, John and Richard 'Kerry' O'Brien Jnr were sentenced to six-and-a-half and five-and-a-half years each. Also jailed were Kerry senior's brother John 'Cash' O'Brien, his nephew Richard Sheridan, and his brother-in-law Danny 'Turkey' O'Brien.
The antique dealer's mansion in Rathkeale had also been raided by the Criminal Assets Bureau as UK police investigated the gang.
Operation Griffin was originally launched after the gang's most successful raid, in which jade artefacts were stolen from the Fitzwilliam Museum in Cambridge.
None of the precious items, which are estimated to be worth €73 million on the open market, have been recovered.
While the headlines suggested the Dead Zoo gang carried out bigger robberies than the infamous Hatton Garden heist, the reality revealed the gang's chaotic and amateurish approach.
Just a couple of weeks before the Fitzwilliam Museum raid the gang had targeted another museum in Durham in which a jade bowl and a figurine worth Stg£2 million were stolen.
The thieves stashed the valuable artefacts in scrubland. But investigators later discovered the gang was not able to find the hiding place and police were able to retrieve the items.
While in both those cases the smash and grab thieves were caught, police wanted to catch those behind the robberies, the people organising the crimes and hiring the thieves.
Police were able to trace a series of phones calls between the thieves and the senior member of the Dead Zoo Gang in the UK and Ireland.
It also revealed a pattern of panic with raids often not going to plan.
One man, even as he was caught by members of the public and museum staff after stuffing a Ming vase into a rucksack, tried to make a phone call to the one of the gang members.
Because of the value of the raids and the involvement of an organised crime gang, senior detectives were assigned to Operation Griffin.
Using their mobile phone records, the investigators were able to link the men to the conspiracy to rob five separate museums.
It also led them to the Dead Zoo Gang's middleman in the UK, Chi Cheong Donald Wong, otherwise known as Donald Wong.
By June 2012, he was under surveillance and on various occasions was observed with different members of the gang.
Wong's trial heard that he submitted modest tax returns but lived in a double-fronted three-storey home overlooking Clapham Common in south London.
Police twice found him with thousands of pounds in cash stuffed in plastic bags.
On one occasion, officers assisting Wong after he was injured in an unconnected attempted raid found a green carrier bag and a black pouch containing £68,000 under the passenger seat of a car.
In July 2012 he was arrested along with Richard Sheridan in London in which police seized Stg£50,000 in cash along with a 'libation cup' made from rhinoceros' horn, which Sheridan had acquired the previous May at an auction in Florida.
The arrest was an occasion where Operation Griffin and Operation Crash would over-lap and come back to haunt Sheridan, a man who had once held himself out a spokesperson for Travellers' rights.
Another of the raids which formed part of Operation Griffin was the attempt to take a rhino head from Norwich's Castle Museum. It was described in court as a fiasco.
Four thieves hired in by the gang dropped the head, which was heavier than they expected, as they ran out of the museum pursued by members of the public.
They also left behind a car number plate complete with an incriminating fingerprint.
The next raid was equally chaotic. Three more hired thieves, posing as customers at an auction house in Lewes, East Sussex in March 2012 jumped over a counter and stole a £20,000 bamboo cup instead of the rhino horn they were meant to take. They too were arrested after members of the public intervened.
Following that botched robbery Detective Superintendent Adrian Greene described how their investigations clearly pointed to another group behind the thieves.
"You start analysing the telephones and that ultimately took us to a call to a vehicle insurance company that gave us the details of Richard 'Kerry' O'Brien Jnr."
Information cross-referenced with historical data held by Europol "highlighted some potential people - mainly the 'Kerry' O'Briens, Michael Hegarty and Daniel 'Turkey' O'Brien".
The trials and convictions of the Dead Zoo Gang attracted worldwide media interest. As well as British and US media covering the story, there were also TV documentary crews arriving from France to find out about the gang.
Richard O'Brien Snr complained bitterly about being unfairly linked to the crimes.
He claimed in an online blog that he had been the victim of discrimination and that his son had been set up by law enforcement. It had emerged during the UK trials the O'Brien family home in Rathkeale had been raided by gardai as part of the investigation.
A notebook and other paperwork were found which had the name D Wong and a mobile telephone number and email address.
"These facts further confirm Donald Wong's links to the O'Brien family," said the Crown prosecutor in his opening address
Even so, O'Brien Snr was unhappy about the coverage and complained journalists had not approached him for his side of the story.
He maintained he is an innocent businessperson who has been a victim of a conspiracy by the gardai and the media to link him to a notorious criminal gang.
He suffered a high-profile legal defeat when a judge in New York dismissed his $18.5 million libel and emotional distress action over an article that linked him to the rhino horn gang.
He had sued Bloomberg Businessweek, which he claimed falsely portrayed him as the mastermind behind a multimillion global criminal conspiracy.
In 2018 he ended up being the subject of court proceedings by the Criminal Assets Bureau in which it won a court order for a car it had seized.
But when approached about the case he did not seem predisposed to discussing the matter with the
He launched a vile, foul-mouthed rant and made threats of violence during the outburst at his red-brick mansion in Rathkeale.
"I'll break your neck you b*****d you!" he shouted. "G'out! G'out! I'll hospitalise you, you c**t you!" he added as a female relative put her arm across him, warning him to calm down.
Just moments earlier the same woman responded with a string of expletives when asked if Kerry O'Brien was home. "F**k out! Move now!" she shouted as she tore up an offered business card.
"He doesn't want to ring you, you put him enough inside in the papers... after all the rubbish you put in the papers?"
At this point Kerry emerged from a foreign registered vehicle in the driveway and began his nasty rant.
Rathkeale's one-time top Traveller trader hadn't turned up in court to stop the CAB from selling off his car, despite claiming to have been set up. At the time he owed an €800,000 tax bill after a garda investigation in co-operation with Europol.
At the CAB court hearing in Newcastlewest, a revenue sheriff sought an order allowing him to sell off the VW Passat. Judge Mary Larkin heard evidence that the English-registered car was seized at the request of CAB in September 2017 in Rathkeale.
The court was told that the case was sent to the sheriff shortly after a "notice of final demand" was served on Kerry O'Brien the previous April.
The €789,291 tax bill included around €290,000 in unpaid taxes plus interest and penalties. Evidence was given that the car was observed by gardai at various locations on dates in 2016 and 2017.
On at least one occasion it was spotted at his Rathkeale home, while on other dates it was booked on a ferry travelling between Dublin and Holyhead.
An unnamed CAB officer told the court he asked the sheriff to seize the vehicle on foot of a warrant which was issued by CAB.
Not long afterwards, his nephew Richard Sheridan was extradited to the US after finishing his sentence in the UK.
The rhino horn he had brought in hand luggage to London from Miami to sell to Donald Wong would cost him more time in jail. He appeared at a Federal Court hearing in Florida where he got another 14 months.
The last time he had been in the famous resort city Sheridan thought he was on to a good thing after paying €57,500 for a rhino-horn cup when he and Michael Hegarty made the trip from London in May 2012.
At an auction house in Rockingham, North Carolina Lot 463 had caught their eye, bringing with them a local resident to get around regulations.
Federal prosecutors said at Hegarty's trial in 2017 that Sheridan acted as the bidder on behalf of three separate bidders, making the winning bid for the 'Chinese Rhinoceros Horn Chilong Libation Cup'.
A couple of days later from his hotel in Coconut Grove in Miami, Hegarty called Federal Express to have the rhino horn cup delivered to him in Florida.
Later that month he put the cup in his luggage and stepped on flight to London, but in doing so he broke US federal law by failing to declare its export to the US Fish and Wildlife Service and he failed to apply for the necessary permits.
Charged with conspiracy, Sheridan entered a guilty plea, having been extradited to the US from the UK.
Hegarty had been jailed for 18 months in 2017 for his role in the scam after being extradited from Belgium where he had been arrested following an Interpol Red Notice.
US Attorney Ariana Fajardo Orshan said after the case that international co-operation is needed to protect endangered species and thanked the European based agencies that helped make the case.
In 2020 the relentless Americans still had someone in their sights.
This time it was the turn of John Slattery, brother of Michael Slattery, who had made the 2010 trip to Texas, to do time in a US prison.
He had been initially identified as a smuggling suspect but had returned to Ireland and changed his name to John Flynn.
He was tracked down by investigators and arrested in France where he got bail before returning to Ireland.
John spent nine months in custody in Ireland when the US sought to have him extradited to face trial.
Eventually he was sent back in May 2022, after the US Marshalls sent a private jet to collect him from Dublin.
At court in Waco, Texas, he pleaded guilty to rhino horn smuggling and was given a 12-month sentence.
Because his time in custody in Ireland had been taken into account, he was deported back to Ireland after three months.
Slattery was the last of the suspects from Ireland the US authorities were chasing. It had taken them ten years to do it, but the message was clear that rhino horn smuggling in the United States would lead to time in prison.
The various police operations appeared to have stopped the Dead Zoo Gang in its tracks by early 2014.
But another court case, this time in France, showed they were still hard at work even when they knew it could attract a lot of police attention.
A hearing in Rennes in 2021 revealed how French police used phone taps and surveillance to nab four Rathkeale Rovers involved in a €13 million rhino horn and elephant ivory smuggling racket.
Two men, Tom Greene (33) and Richard O'Riley (35), described as brothers, were both given prison sentences in their absence at a criminal court in Rennes.
These are aliases used by the men who are related to others who have been imprisoned in the UK and United States for their roles in rhino horn smuggling, according to
Sunday World sources. Both men are related to the 'Kerry' O'Brien family.
Two other Irish men named in the court proceedings, Edward Gammel (33) and Daniel McCarthy (29), were also convicted for their parts and given suspended sentences.
Customs fines of up to €200,000 were also imposed on each of the men and they could face extra time in prison for not paying if arrested in France.
The case highlighted how the Dead Zoo Gang were still at work chasing profits despite its leading figures being jailed in the UK at the time in 2016.
'Tom Greene' was singled out as the leading figure in the plot which also saw four Franco-Chinese men convicted over the illegal export scheme. He got a three-year sentence despite the public prosecutor calling for a six-year term and referring to Greene as 'a hunter without a rifle' and the gang's 'sales rep'.
French prosecutors started their investigation after a random motorway traffic inspection by police in Poitiers in September 2015 that led to the discovery of several elephant tusks and €32,800 cash in a BMW.
The occupants of the car, who claimed they were antique dealers, were the four Irish men with addresses in the UK and Ireland.
In May 2016, investigators from the National Judicial Customs Service seized 14 raw ivory tusks of African origin and two carved tusks without any document as to their legal origin at a warehouse in Seine-Saint-Denis, north Paris.
On November 15, 2016, in a room of a B&B in Creil near Paris, Greene and O'Riley were arrested again with a rhinoceros horn weighing 14.7 kg.
The seizure took place close to a Chinese restaurant whose manager is one of the other convicted men. All four Irish men were convicted in their absence and warrants issued for the arrests of Greene and O'Riley who was sentenced to a year behind bars.
The trial in Rennes highlighted how the Irish men had forged close links with European based business people with direct links to the Chinese and Vietnamese market.
French police also discovered that ivory and rhino horn were being turned into powder and flakes on French soil before being exported to Vietnam and China.
A Chinese businessperson, David Ta (51), was given two years for his part in exporting the horns and tusks.
Photos in Mr Ta's phone had enabled investigators to count 62 tusks that passed through his company between November 2015 and April 2016. Three other Chinese men were also convicted for their parts in the smuggling ring, including one described as Greene's biggest customer.
The poaching of rhino horns in Africa hit a peak in 2015 at 1,349, according to the Save The Rhino organisation. The crisis, sparked by the demand from China and Vietnam, began in 2008.
The numbers of animals being poached has dropped since the peak, but remains higher than it was pre-2008.
The demand still exists and if the opportunity arises the Dead Zoo Gang will not miss their chance.
They remain involved in cigarette smuggling via Luxembourg and Belgium.