A police officer who shot dead a mentally ill young man armed with a bread knife will not be charged, the Director of Public Prosecution has confirmed.

In a statement released this afternoon, the DPP said that after 15 months of consideration they have decided not to commence proceedings against Senior Constable Andrew Rich for murder or manslaughter following the death of Elijah Holcombe in 2009.

Mr Holcombe, 24, a graduate of Macquarie University, was suffering from a mental health breakdown characterised by episodes of paranoia and delusions when Senior Constable Andrew Rich and Senior Constable Greg Dufty were asked to find him and take him to Armidale Hospital, where nursing staff were concerned about his welfare.

But when the plain-clothes police officers approached Holcombe on June 2, 2009, the student ran away.

Constable Rich pursued him on foot before Holcombe armed himself with a bread knife and ran into a laneway.