Detectives believe that a man who was found with life-threatening head injuries in Whitworth Park was the victim of a serious assault.
Shortly before 8.50pm on Tuesday 11 September 2012, police were called to Whitworth Park, Manchester, following reports of a man being injured.
Officers attended and found a 38-year-old man with serious head injuries.
He was taken to hospital and heavily sedated. While he has stabilised, he remains in a critical condition.
The head injuries themselves are believed to have been caused by blunt force, which would suggest he was hit on the head with a weapon.
Detective Inspector Theresa Carter said: "Since we found this man in a life threatening condition, a number of inquiries have been made to find out what happened.
"We now believe that he was the victim of a vicious assault and was hit with a weapon.
"I would therefore like to appeal to anyone who was in the park from early evening until 9pm on 11 September, to come forward and tell us what they saw.
"We understand that the victim is homeless and as such we have been speaking to others who sleep rough in this area.
"He was last seen at a day centre on Denmark Road at 11am on 11 September.
"I would ask that anyone with information calls police as soon as possible."
Anyone with any information is asked to call police on 0161 856 4146 or the independent charity Crimestoppers, anonymously, on 0800 555 111.