Thousands of immigrants are being “picked up off the streets” in the United States and are being held in federal detention centres under the new administration, a leading juvenile justice lawyer has told a conference on family law and children’s rights in Dublin.

Marsha Levick, deputy director and chief counsel at the Juvenile Law Centre in Philadelphia, said President Donald Trump’s administration is “taking a different tack” on immigration.

She said her organisation has been getting reports of “thousands of individuals who are being picked up off the streets and detained in federal detention centres by our immigration force”.

“What is more troubling for many of us in the States is that those facilities are being run by private for-profit providers, something that the current administration also supports the expansion of,” she said. “When you make jailing profitable, you can be sure that more people will be jailed.”

Speaking at the World Congress of Family Law and Children’s Rights in Dublin, she also told delegates from 53 countries that the Obama administration had introduced a complete ban on the solitary confinement of children in federal prisons, which are run centrally by the US department of justice.

“That ban hasn’t been withdrawn yet; are we worried that it will be? Yes, that’s where we find ourselves,” she said.

A quarter of world prisoners The congress, in Ireland for the first time, features 150 speakers over four days, with more than 600 delegates expected to attend.

Ms Levick said the US houses 25 per cent of the world’s prisoners, while having 5 per cent of its population.

In any one day, there are 60,000 children in custody. The system is also “largely populated by black and brown children”, she said.

She said Americans believed in the concept of “due process” but “it is as often breached as it is followed”. There were 51 jurisdictions in the US, she said, with 51 different juvenile justice systems.

She said that somewhere in the US today, a teenager was locked in solitary confinement in a 7ft by 10ft room; somewhere in a juvenile prison, guards were using pepper spray to control children and requiring them to shower afterwards to “make the consequences worse”, because water increases the effects of the spray; somewhere else, a 12-year-old child was being strip-searched and made to “squat and cough”.

She told the congress that although the US had signed the United Nations Convention on the Rights of the Child, it had not yet ratified it, the final step towards legal enforcement, as it still had some concerns with some elements of the convention.

Guess who suffers At a separate congress session, Dr Robert Simon, a forensic psychologist from San Diego, California, spoke about the dangers of family courts hearing “a single narrative” about families.

He said our lives, cultures, relationships and families are composed of many overlapping stories, but professionals easily fall into the trap of single stories.

“The human brain is designed to oversimplify things that are complex . . . This leads to stereotyping,” he said.

Dr Simon said in order for professionals to fight for their clients, they often stereotype the other person, but this robbed them of their dignity.

“I think of a courtroom as one of the world’s most powerful theatres, and we decide the narrative,” he said.

He said the person who writes the most convincing story is most likely to succeed. Narratives in the courtroom had to be based on truth, he said, but also had to leave room for healing.