A Belfast DJ who died after an incident involving police was struggling for his life while being restrained, an inquest heard.
A coroner is investigating the circumstances surrounding the death of Gerard McMahon.
The 36-year-old, from the Short Strand, died hours after he was held in a prone position by three PSNI officers restraining him on September 8, 2016.
Yesterday one of the officers involved, referred to as Officer B at the inquest, said that when he arrived at the scene around one minute behind his colleagues, named as Officer A and Officer C, he had assessed Mr McMahon as being under the influence of alcohol and drugs.
He also said he considered the possibility that Mr McMahon could have been suffering from Acute Behavioural Disturbance (ABD).
This is a condition brought on by mental health issues or as a result of cocaine use. Symptoms can include bizarre and erratic behaviour, profuse sweating and violent outbursts, following a period of calm.
The inquest, sitting in Belfast, heard that Mr McMahon had the condition and that as such he should not have been placed in the prone position which left him particularly vulnerable to positional asphyxiation.
The inquest heard how the three officers restrained Mr McMahon on the ground after he became agitated and aggressive as they feared he would escape, with Officers A and B at his two shoulders while Officer C held his legs and applied limb restraints.
In his evidence, Officer B confirmed to the coroner, Joe McCrisken, that he had put his right knee on Mr McMahon's back at his left shoulder while he was being restrained on the ground, saying: "I felt that at the time we were losing control of him with just my hands."
Officer B, responding to questions posed by the legal representative of Mr McMahon's family, said that in the midst of the struggle and restraint of Mr McMahon, he wasn't thinking that he had ABD or that he was at increased risk from positional asphyxiation because of it.
When asked if he appreciated now that "while this man (Mr McMahon) is struggling for his life, you are struggling for control" Officer B said he did, although at the time, he thought Mr McMahon was struggling to escape.
Efforts to administer first aid to Mr McMahon were unsuccessful.
The inquest continues.