Greater Manchester Police illegally used CS gas grenades for five years, it has emerged. Britain's second largest police force bought CS Dispersal Canisters (CSDC) between 2007-2011 despite them not being tested and approved by the Home Secretary.
The details emerged at the public inquiry into the fatal shooting, by a police marksmen, of Anthony Grainger in 2012.
Grainger was killed by a single bullet to the chest as he sat in a stolen Audi with two other men in a pre-planned police operation. He was unarmed.
CS gas – a powerful form of tear gas – was also used in the operation and is why the revelations came to light.
Jason Beer QC, counsel for the inquiry, said GMP had not followed the proper process and used only their own testing procedures.
"It is clear that the CSDC first introduced by GMP in 2007 was not approved for use by the Home Secretary. That much is now admitted by GMP as we may hear.
"An issue may fall to be determined as to whether GMP consciously breached the code of practice, knowing what it was required to do by the law but deciding not to do it, or whether GMP did not know of the requirements of the code of practice or whether GMP believed that it had acted in accordance with the law," said Beer.
The inquiry will now widen its scope to look at GMP's use of the CS grenades.
"This may raise issues for GMP which extend beyond the use of CSDC on 3 March, including, first, whether GMP knew that its use of the CSDC between 2007 and 2012 was without the approval of the home secretary," Beer added.
"Second, why GMP introduced the use of the CSDC without the approval of the home secretary, without taking any of the steps required by the statutory code of practice to secure such approval and in breach of the statutory code of practice.
"Third, what steps GMP took after a member of the National Police Improvement Agency advised GMP in 2009 that its use of the CSDC was dangerous."