The mother of a boy who died after being pushed into a river has begun her High Court battle against the decision not to prosecute the teen accused of being responsible.

Christopher Kapessa, 13, was allegedly pushed into the River Cynon near Fernhill, Rhondda Cynon Taff, by a 14-year-old boy in July 2019, but the Crown Prosecution Service (CPS) decided not to charge the teenager, saying it was not in the public interest.

Christopher’s mother, Alina Joseph, from the Cynon Valley, has launched legal action against the Director of Public Prosecutions Max Hill, who heads up the CPS.

Lawyers representing her challenged the CPS’s decision at a hearing in London on Thursday, with Michael Mansfield QC telling two judges it was “unreasonable or irrational”.

“The defendant’s decision fails to properly value human life, specifically the child victim’s life,” he told Lord Justice Popplewell and Mr Justice Dove in a written case outline.

“The defendant fails to give proper regard to the seriousness of harm from the offence.”

He added: “Undue and improper weight has been given to the impact of a prosecution upon the future of the offender.”

Mr Mansfield said the message the decision sent out did not inspire confidence in the justice system.

He said evidence existed to provide a “realistic prospect” of conviction for manslaughter.

The judges were told 16 people were at the scene of Christopher’s death.

Mr Mansfield said Christopher had expressed concerns about his lack of swimming ability and had been “unwilling to enter the water freely”.

He added: “The suspect pushed him deliberately into the water.

“Christopher drowned and was killed as a result.”

He said Christopher and his family were “relatively new” to the area and were a black family living in a predominantly white community.

Judges ruled the suspect cannot be identified in media reports of the case.

Mr Mansfield argued the decision not to prosecute was “unlawful” and “ought to be quashed”.

He said the “suspect” was now 17.

“One factor – the youth of the offender – has been given too much weight here,” he added.

“The suspect in this matter is aged 17 presently, but that does not preclude the public interest in accountability for causing a death by unlawful act manslaughter.

“It would not be ‘disproportionate’ to prosecute a child or young person for the manslaughter he has committed.

“The youth of the offender is a factor that a criminal court itself may properly take into account when imposing punishment…”

Mr Mansfield said Ms Joseph had given detail of the information she had received, in a witness statement.

He told judges, in a written case outline: “This sets out the history of misinformation to her from the investigating prosecutorial authorities since her son’s death and concerning the events: the original source of being told her son had jumped, or had slipped, rather than being pushed appearing to have emanated from the suspect and the untruths spread by him and his immediate friends, including the lies told to the police.”

Mr Mansfield said she wanted to “understand fully what had happened to her son” and to “see justice done according to that truth”.

The CPS said in July 2020 the evidence suggested Christopher had been the victim of a “foolish prank”.

Jenny Hopkins, who then oversaw the CPS appeals and review unit, said at the time: “Although there was evidence to support a prosecution for manslaughter it was not in the public interest to prosecute

“Christopher’s tragic death occurred after a group of children went out to have fun by the river.

“The evidence showed that Christopher was pushed into the river as a foolish prank with nothing to suggest that the suspect intended to harm him, although that was the awful consequence.

“Factors we took into consideration when reaching our decision included the young age of the suspect who was 14-and-a-half at the time, his lack of a criminal record, and otherwise good character.

“Significant weight must be attached to the age of a suspect if they are a child or young person under 18.

“In that context we also considered the impact on his future prospects and that the main aim of the youth justice system is to prevent offending.

“We also considered the impact of a trial on the other children who were present.”