There had been a gradual decrease in the number of people in custody in the State.

In 2011, the daily average number in custody was 4,390. This reduced to a daily average of 3,680 in 2017, a decrease of 16%. Since last September, there has been an increase of 12%. (The Irish Prison Service puts the increase at 9% since October).

On 4 September last year, the number of people in custody in prisons stood at 3,520. By April 17 this year, that number had increased by 418, to 3,938.

By any standards, that is a considerable increase. Half of the State’s 12 adult institutions — including for male and female inmates — are now operating above the recommended capacity.

In Cloverhill prison, the numbers in custody over the last six months has gone from 312 to 422. It is now operating at over 100% of the recommended capacity.

Cloverhill deals with remand prisoners and an increase in defendants failing to secure bail may partially explain the spike here.

The number detained in Limerick’s female prison has gone from 20 to 37, bringing its operational capacity from 83% to 154%. In fact, the worst of the overcrowding is being borne in the female prisons of Limerick and Mountjoy, the latter operating at 154% of capacity.

On the face of it, these numbers may not appear to be large, but overcrowding in today’s prisons is a recipe for

disaster, both in terms of potential violence and in the courts.

Overcrowding increases tensions and, since the 2014 Equality and Human Rights Act, prisoners may have recourse to the courts, if they believe their rights are being abused through unsafe forms of detention.

There is also an issue around whether the various prisons currently have contingency cells, in the event of a disturbance or a fire.

Then there is the problem with Cork Prison. Since it was opened in 2016, it has become obvious that the city’s €45m prison is barely fit for purpose.

The capacity of the new prison was constrained by site issues and, not least, political considerations.

A long-term plan to build a new prison in Kilworth, in the north of the county, was shelved in the wake of the huge controversy over the building of a prison in Thornton Hall, north County Dublin.

Humanitarian concerns — in both cases, the respective prisons were a good drive from the cities, where most prisoners’ families lived — along with financial problems ensured that the plans didn’t go ahead.

Instead, the new facility in Cork was built down the road from the existing prison, but many within the service are now questioning the wisdom of the move.

Since it was opened, the new prison has had problems accommodating all committals from its designed catchment area in the south of the country. Its capacity has gone from 264 inmates to 280 and is now operating at 95%.

According to reports, some committals have been redirected to Limerick, because of capacity issues.

In the bigger picture, no definitive reason has been identified for the spike. Deirdre Malone, director of the Irish Penal Reform Trust, said that they have not yet ascertained the reasons for the rise.

We would be particularly worried, if standards [of detention] were being affected, as we have had a period where standards were kept-up and we will have to see how that goes.

Sources in the service have offered various reasons for the spike. One is that the policy of imprisonment as a last resort for failure to pay fines replaced the old one of prison as the first port of call.

That policy has been welcomed, but there is speculation that some of the spike may be attributable to the small number who have arrived at at the last resort of imprisonment.

“The fines act was a good move. It freed up spaces and gave people an opportunity to pay,” according to one source in the prison service.

Prison became a last port of call rather than a first, but it could be that those who have been given every other chance to address fines, and haven’t, are now reaching the point where they are being committed anyway.

Whatever the specific reasons, there should be some urgency in addressing the spike. If the trend were to continue — and reversing it is unlikely to occur overnight — then, by the end of the summer, the prison population will have increased by around 800 in 12 months, enough prisoners to fill a large prison in itself.

All the more reason to identify why the current spike is occurring and how best to address it.