Barry Imray, 35, of no fixed address, is jointly accused of killing Lee Irving, who was found dead near a footpath in Newcastle last year.
James Wheatley, 29, from Studdon Walk, also denies Mr Irving's murder.
Mr Wheatley's mother, Julie Mills, 51, and his girlfriend, Nicole Lawrence, 22, are accused of "causing or allowing" Mr Irving's death. All four deny the charges against them.
Mr Imray told Newcastle Crown Court he had seen Mr Irving with facial injuries a week before his death.
When asked by his defence counsel how he felt on finding the 24-year-old apparently lifeless a week later at the house they shared in Kenton Bar, he said he had been "scared".
Jamie Hill QC asked Mr Imray if he had "done anything" to Mr Irving, such as hitting him or kicking him, to which he said no.
It is alleged Mr Irving, who had learning difficulties, had been sedated by the defendants, rather than taken for medical treatment.
The court heard how he had been found about half a mile from the house with 27 rib fractures and a broken nose and jaw.
The trial continues.
A man accused of murder has told a court he is "easily led".