Greater Manchester Police, and two police officers, will be charged today over the death of PC Ian Terry during a police training exercise.
On Tuesday the Crown Prosecution Service said there was insufficient evidence to prosecute the GMP or the two officers with criminal charges.
However the Health and Safety Executive have said that there is sufficient evidence to charge them under health and safety laws.
PC Ian Terry was fatally shot as Greater Manchester Police's firearms unit practised in a disused factory in the city on June 9, 2008.
Terry, 32, from Burnley, Lancashire, was armed with an unloaded handgun during the exercise while playing the role of a criminal fleeing in a car.
On seeing him holding the gun, his colleague acted "instinctively" and pulled the trigger on his Remington 870 pump action 12-bore shotgun.
Terry, who was not wearing body armour, was hit from a distance of about 12 inches by a blank round of a specialist ammunition called Round Irritant Personnel (RIP), designed to burst tyres and break windows and deadly at close range.