An unemployed electrician was yesterday ordered to be detained indefinitely at a secure hospital after killing a 16-year-old girl as she sunbathed in a city centre.

Inderjit Kainth, 44, denied the murder of Rosie Ross but pleaded guilty to her manslaughter due to diminished responsibility.

Birmingham Crown Court heard that Kainth, of Uplands Road, Handsworth, Birmingham, was suffering from paranoid schizophrenia at the time of the attack in May this year.

Rosie, of Aldridge, near Walsall, West Midlands, was stabbed to death in Birmingham's Centenary Square as she relaxed with a female friend after a shopping trip.

Making the hospital order, Mr Justice Eady said it was clear Kainth was, and was likely to remain, a serious danger to the public.

He told him: ''I am satisfied that you were suffering from a mental illness, namely paranoid schizophrenia. It is also clear to me that it is necessary for the protection of the public from serious harm that a restriction order should be made under section 41 of the Mental Health Act 1983 without limit of time and with maximum security.''

The judge added that Kainth, a divorced father-of-five who has competed in more than 150 marathons, would only be released if the home secretary or a mental health review panel deemed it suitable.

Chris Millington QC, prosecuting, told the court that Rosie was stabbed in the stomach with an eight-inch carving knife as she lay on a wall in Centenary Square on May 12.

Kainth, looking ''oddly out-of-place'' in a leather jacket despite the early summer heat, approached the popular schoolgirl.

He then produced a sheath, fashioned from a shampoo bottle and containing a black-handled knife wrapped in a black bin liner, and stabbed the teenager.

Three people in the busy square, near the International Convention Centre and National Indoor Arena, chased Kainth as he fled towards the Birmingham Canal and dropped the weapon into the water.

The men, Matthew Brown, Cain Jason and Marcus Freckleton, then dragged Kainth back to the scene where Rosie was being attended to by two doctors.

Mr Justice Eady praised the trio for their ''considerable presence of mind and courage'', while police said after the case that they would be officially recognised for their actions.

Mr Millington said: ''Kainth had paranoid delusions that he was being persecuted. He believed the only way to save himself was to kill a woman. He had been looking for a victim for several weeks.

''He was talking about the Civil Service out to kill him. He was calm, he showed absolutely no regret for what he had done. In fact, he seemed somewhat relieved.''

The lawyer also revealed that in the weeks before the tragedy, Kainth had made repeated visits to West Midlands Police's Tally Ho training centre in Edgbaston, Birmingham, with the intention of killing a policewoman.

Punjab-born Kainth, who was warned away from the centre, later led police to a flowerbed in Colmore Circus, Birmingham, where he had concealed a knife.

Psychiatric experts also discovered that Kainth was obsessed with a girl he had had a brief relationship with as a 10-year-old schoolboy, which he claimed had been ended by school authorities.

He had even travelled to Canada, where he believed she now lived, to find her and the only way to get her back was to ''take revenge by killing somebody'', the court heard.

Adrian Fulford, defending, said Kainth had since expressed regret for his actions.

He added: ''We wish to say on his behalf to the family of the deceased that this happened, this sad and tragic event, took place because he was seriously mentally unwell at the time.

''His lack of remorse at the time, we hope, is understood in this context.''

Detective Inspector Gary Campbell, of West Midlands Police, said Kainth had shown no signs of mental illness in the years before the attack and had led a ''quiet, unremarkable'' life.

Mr Campbell added: ''It is one of the most serious and worrying aspects to any future release that he was able to operate up to a few months before Rosie's (death) without anybody knowing the thoughts and feelings he was having or what was going to follow.''