The man accused of brawling with Sheku Bayoh hours before his death has angrily denied the claims, saying there is "no possibility" he caused his injuries.
Zahid Saeed, 31, had been long-time friends with Mr Bayoh and admitted to being involved in a physical altercation with him in the hours before he died in police custody.
However, he is adamant he did not strike the father-of-two and cause him any injuries.
Mr Bayoh was pronounced dead around two hours after nine officers restrained him on a Kirkcaldy street on May 3.
Mr Saeed, whose three-year-old son Mikaeel Kular was killed last year, said his friend had been helping him to come to terms with his own grief.
He told a Sunday newspaper: "As the night wore on, Sheku was acting out of character... It’s the only time I’ve seen Sheku act in such a way. People may question this but it is simply the truth.
“I caught up with Sheku at his house and, at this point, I tried to calm him and he lashed out at me. It appeared as if he was scared or upset.
“He punched me a few times on but I did not hit him once and am extremely angry at any suggestion or inference that I did.
“It is an attempt to plant a seed in people’s minds that the many injuries found on Sheku’s face, head and body could have been caused by something other than his contact with police."
Mr Bayoh, also 31, was restrained by up to nine officers using CS spray, batons, wrist and ankle restraints and was pronounced dead two hours after coming into contact with police.
The father-of-two did not have a knife when apprehended but one was recovered next to the scene.
A female officer was injured during the incident.
Last week, a police source said that Mr Bayoh's death could have been avoided had officers had access to Tasers that morning.
Inquiries are ongoing to establish the cause of death after an initial post mortem examination, which said he had taken ecstasy, proved inconclusive.
Mr Saeed said he was questioned by police shortly after Sheku's death and claims he had his DNA taken, while his clothing and mobile phone was confiscated.
He said: “I was treated in a very hostile manner by police. This is despite them knowing Sheku had died after being restrained by their officers.
“I wish to be very upfront about what happened and it is true that Sheku was acting out of character that morning. There is no possibility I inflicted any cuts, lacerations or broken ribs on him.”
Mr Saeed, revealed that Mr Bayoh and his partner Collette Bell gave their son Isaac the middle name Mikaeel as a tribute to the three-year-old.
He said: "Sheku helped me through the darkest moments of my life when Mikaeel died.
“He called me, helped me and held me when I was crying after my son passed away.”
Meanwhile, Mr Bayoh's family have accused Police Scotland of trying to remove evidence by trying send his body to Sierra Leone.
On May 5, investigators are said to have contacted the Sierra Leonean Embassy in London to discuss ‘repatriating’ his body to the country of his birth.
Mr Bayoh's brother-in-law, Ade Johnson, 38, said: “Why was Police Scotland looking to send Sheku’s body out of the country without consulting his family?
“That is not the action of a police force with nothing to hide.”
Police Scotland, the Crown Office and the Police Independent Review Commissioner, which is tasked with reviewing Mr Bayoh’s death, all said they could not comment on matters relating to live investigations.