The child's no older than four. Old enough to master the art of imitation but not yet of an age to fully understand what his gesture represents. Atop sturdy shoulders at the funeral of Limerick criminal Philip Collopy – who shot himself accidently in the head 15 days ago – the child's message is all the more poignant. His extended middle finger is a symbol known to the whole world.

"If he does that of his own volition now, what might he be doing in a few years time?" asks garda Jerry Scanlan, a juvenile liaison officer (JLO) in Limerick. He works with children and teenagers who get into trouble with the law and tries to keep them out of the revolving-door court system through intervention.

"If he has that hatred and disregard for society now, we'll be seeing that child in a few years' time. I've no doubt in my mind at all. I'm beginning to deal with the third generations of men from the same families in Limerick. I'm now dealing with the grandsons of men who I dealt with when they were getting into trouble."

Scanlan has called to the houses of some of the major crime families in Limerick when one of their children has been caught breaking the law. It could be for something as minor as bunking off school, or it could be for being caught in possession of a sawn-off shotgun. "In the majority of cases, the parents don't want to see their children go down the same path as they did, in and out of prison. But I have seen cases where the parents aren't bothered. It's a game for them and they play it. Crime is a way of life for some families and not just in Limerick."

Infamous imprisoned Dublin criminal Tony Felloni, the man responsible for flooding the capital with heroin in the 1980s, is the extreme example of a father hell-bent on passing on his trade to his offspring. He enlisted his children to help him sell heroin when they were just teenagers and actively encouraged some of them to experiment with the drug, earning him the name King Scum.

The authority and strength that criminal families represent has been glorified by the Sicilian mafia and is being mimicked by young criminals here. Gangster rap music from the US has also become a major influence, with many teenagers involved in criminality dabbling in hip-hop expression to discuss violent life in Ireland. A scan of Bebo social networking sites of teenagers on the outskirts of crime here reflects their obsession with, and emulation of, all things gangster-related. On the 'Limerick City Mafia' Bebo page, the welcome message reads, "Live by da gun, die by da gun. Don't f*** with the city mafia", alongside an illustration of three gangsters, one of them brandishing a shotgun. Someone has left a telling message on the site: "There's no mafia in Limerick dude. Big shout out to all the little scumbags who think they're gangsters."

On 'Da Dublin Gangstas' Bebo page, a photograph of two semi-automatic guns greets visitors as gangster rap music plays in the background. Other Bebo pages show photos of crime scenes complete with victims in body bags, houses on fire and photos of large quantities of drugs. On many of these sites, there are tributes to friends who have died, many of whom have been murdered while still in their teens.

"The internet has provided so much information for this generation of young people, and through self-expression on Bebo and these other sites they can highlight their admiration of mafia culture. They see it as a lifestyle choice," explains Jonathan Culleton, a lecturer in sociology and criminal justice at Waterford Institute of Technology's (WIT) centre for social and family research. "'Get Rich or Die Trying' is the saying and the attitude that's been adopted, it's a very nihilistic one. It shows an unwillingness to engage. Some of these young people are saying they look at their existence as a 'kill or be killed' situation."

While the criminality these young men boast of on the internet may be exaggerated to reinforce a tough-guy image, their romanticising and imitation of mafia culture cannot be ignored.

In Ireland today, organised criminal families have emerged as stronger entities in Limerick than in Dublin, evident from the Keane and Collopy families' ongoing feud with the McCarthy and Dundon crime gang. This is mainly because of the smaller size of Limerick – geography has forced allegiances between criminals to strengthen because there are fewer gang options. Like the mafia, criminal families here enjoy some support in their communities and often feel superior to the average criminal.

"There's often a Robin Hood element with some of these crime families. The local community know these people. They are not outsiders. There is often gift giving to maintain the illusion that 'these are our people'. It happened with the Colombian mafia and I'd say it's happened in Limerick too," Culleton says.

"Martin [the General] Cahill was great at that, creating this image of a lovable villain. There is also a certain moral element within crime families. It might be hard to convince your kids to rob a post office but if it's for the good of the family, that's very persuasive. Also, there is usually a much greater trust between family members involved in crime than criminals who are part of the same gang. The Omerta code [mafia code of silence when questioned by police] is naturally stronger among family members."

While criminal families in Dublin exist, they have developed more through sons mimicking the behaviour of their fathers, brothers and cousins than in the structured way evident in Limerick. John Daly, the young Dublin criminal murdered in 2007 whose call to RTÉ Radio's Liveline provoked a clampdown on mobile phones in prisons, was always trying to live up to his father's tough-guy image, according to a source. But his natural criminal progression was to become a member of the infamous Finglas gang the Filthy Fifty, rather than involve himself with family-based crime.

Statistically, the number of gangland murders in the capital dwarfs the killings in Limerick, yet the latter often grabs the headlines. The breed of criminal that has developed in Dublin is strongly individualistic. These men – and it is always men – are willing to murder their associates if needs be, are motivated solely by profit and generally avoid the media glare.

The reasons why a child born into deprivation in certain parts of Ireland has the odds stacked against him are as glaring as they are depressing. Urban working-class areas around the country were effectively abandoned by the state decades ago and only now are attempts being made to rectify the social problems that developed in these trouble spots.

"Decades ago, the state moved some inner-city tenements to modern, new green areas on the outskirts of cities, such as Ballybeg in Waterford and Ballymun in Dublin. It was seen as a very attractive alternative at the time but these places effectively became holding pens. They provided no support or services to the communities in these areas," says Culleton. "It's a legacy of past public-policy mistakes. If you continuously neglect an area, there's a price to pay. We're paying it now. I'm not a believer in the notion that you can be born a criminal. Almost all of the time, the reasons people become criminals is because of the society they live in."

Depending on where someone is born, certain things are expected of them by society. It can vary from the family tradition of entering politics to becoming a skilled armed robber. "It can become a rite of passage for some children to spend time in prison whereas it would be a source of shame and embarrassment for someone from a more affluent area," says Ian O'Donnell, a criminologist at UCD. "But white-collar offenders are not born into deprivation. They are born into privilege and their involvement in crime is less about pre-destiny and more about opportunity. But the garda focus is on low-level crime and violence, leading to inequality."

Parish priest Fr Séamus Ahern has been based in Finglas for 12 years and has presided over the funeral masses of many gangland victims, some of them murdered while still teenagers.

"I can look at the children in this area and predict the ones that will carry on the family involvement in crime," he says. "I see some families involve their children. It is what they bequeath them. It's their legacy. It's almost all they know."

Family crime dynasty The Dunnes

When heroin dealer Larry Dunne (60) was jailed in the 1980s for his crimes he warned that if we thought he was bad we should see what was coming up behind him.

The Dunne family introduced heroin to communities in Dublin and hooked generations on the deathly charms of smack.

Gardaí have since agreed that the drug-dealing boss's prediction was right – Tony Felloni took his place.

Dunne and his family were the first big-time heroin dealers in Dublin during the '70s and '80s. One of 16 children, Dunne emerged as the godfather of the clan and the majority of his siblings became major players in the criminal underworld, later to be convicted of heroin-related offences.

At one stage, the Dunne family controlled 50% of the heroin traffic in Ireland. At the height of his notoriety, Dunne moved from his terraced home in Crumlin to a mountainside mansion in Sandyford, south Dublin.

Even Dunne's wife Lily was imprisoned for selling heroin before her death in 2000.

Dunne's 28-year-old daughter and brother both died of Aids after becoming drug addicts. His nephew Abe Turner, dubbed Prince Scum, also made millions from drug dealing.

King Scum Tony Felloni

Infamous imprisoned Dublin criminal Tony Felloni – the man who flooded the capital with heroin in the mid 1980s – was determined to pass on the family business to his offspring.

He enlisted his children to help him sell heroin when they were just teenagers and actively encouraged some of them to experiment with the drug so he could always control them, earning him the name King Scum.

The 66-year old could be released from Portlaoise Prison next year after serving most of the last 30 years behind bars.

The gangster was hated during the 1980s and was one of the Dublin's main dealers.

But it was his brutality towards women and his family that earned him the nickname King Scum. Ann, his second-oldest child, became a heroin addict while she was still in school and contracted Aids. Her eldest brother Mario Angelo started in the family trade when he was just a teenager. At the age of 16 his father gave him his first taste of heroin in the guise of a birthday present.

Of his eight children, five have spent long spells in jail and others have become heroin addicts.

Felloni also beat his wife Anne so severely on several occasions she had to be hospitalised.