The current site of New Scotland Yard, the headquarters of the Metropolitan Police Service. (Photo: David Holt via Wikimedia Commons)

More than 30 criminal investigations - including 21 rape and sex assault cases - are being urgently reviewed after Scotland Yard admitted one of its forensic scientists could have botched vital examinations.

A total of 33 cases, dating back to 2012, could have been compromised after the scientist allegedly failed to carry out vital tests and also lied to detectives about her work.

The scientist at the centre of the scandal was suspended in March after the issue was discovered during a performance review.

A Scotland Yard spokesman said an urgent investigation into all the cases was now being carried out with those affected being contacted by specialist officers.

But it remains unclear whether any of the cases involved resulted in suspects being wrongly convicted or victims being denied justice.

While the majority of the cases involved sex assault allegations, there were also a dozen relating to violence, burglary and drug offences.

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