Police and university officials struggled to explain yesterday how Cho Seung Hui was allowed to remain at Virginia Tech after he was declared “mentally ill” and “an imminent danger to others” nearly 18 months ago.

As more teachers came forward to say that they had raised concerns with officials as long ago as 2005 over Cho’s violent and sexually disturbed writings, Tim Kaine, the Governor of Virginia, announced an independent review of how the police and university dealt with the massacre, and why Cho appeared to have been unmonitored despite his treatment in a mental health facility in December 2005. “Why he slipped through the net is a very valid question,” Mr Kaine said. “The team will be looking into aspects of this troubled young man who received treatment in some instances.”

As new details emerged of Cho’s evaluation as dangerously mentally ill in 2005, officials sought to blame their inaction on state and national laws, which make it virtually impossible to expel a student.

In October 2005 Cho’s bizarre behaviour and graphically violent writings in his English classes had led at least four of his teachers to report concerns to university authorities. One professor, Nikki Giovanni, threatened to resign unless Cho was dropped from her class. On November 27, 2005, a female student complained about Cho to Virginia Tech police after he sent her troubling instant messages, followed by an unannounced visit to her room. Police interviewed Cho and warned him to stop. A month later, on December 13, another female student complained to police about Cho. One message he sent quoted Romeo and Juliet, saying: “By a name, I know not how to tell who I am. My name, dear saint, is hateful to myself, because it is an enemy to thee. Had I it written, I would tear the word.”

At the same time, one of Cho’s room-mates contacted police to say he believed he was suicidal. After a hearing on December 13, a magistrate ordered that Cho undergo an evaluation at Carilion St Albans, a private psychiatric hospital. He declared Cho to be “mentally ill” and an “imminent danger to self and others”. Cho agreed to attend the evaluation.

The next day, a doctor examined Cho, concluding that his “affect is flat. He denies suicidal ideations. He does not acknowledge symptoms of thought disorder. His insight and judgment are normal”.

Judge Paul Barnett signed an order recommending only outpatient treatment. He ticked the box that Cho was an imminent danger to himself — but not the box saying that he was a danger to others. Cho stayed one night at the clinic and left the next day.

When Cho came to buy the two guns he used in the massacre, in February and March this year, he was legally permitted to buy the weapons, despite the mental health evaluation. Background checks on gun buyers search only for people involuntarily committed to psychiatric wards. As Cho attended the clinic voluntarily, his record came up clean.

“How can a mentally ill person get a gun?” Fred Kosnac, a Virginia Tech accounting student, asked.

Neither female student pressed charges. For all the interventions by police and teaching staff, Cho was not only allowed to remain on campus but carried on life without supervision. Edward Spencer, a senior Virginia Tech administrator, said there was no central file on Cho.

A range of laws also tie the hands of university authorities to expel students, unless they make direct threats or are caught cheating. They cannot release a student’s medical records without consent, and they cannot place a student on leave even if they develop a severe mental illness.

They are forbidden from screening students for psychotic medication, or asking questions about their mental health history.

Last month Virginia became the first state in the US to pass a law prohibiting universities from expelling or punishing students for attempting suicide or having suicidal thoughts.

When Lucinda Roy, a Briton and head of the English department, sent Cho’s writings to police in late 2005, no action was taken. Wendell Flinchum, chief of the Virginia Tech police, said they came from a creative-writing class, adding: “The writings did not express any threatening intentions or allude to any criminal activity, and no criminal violation had taken place.”

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