A Hells Angel accused of attacking a biker outside a pub told a court he watched in "shock horror" as the victim's head "ricocheted" off a wall.
Oliver Wilkinson from St Leonards and Matthew Barnes from Hastings deny grievous bodily harm with intent.
Taking the stand, Mr Wilkinson said it was Sussex chapter president Mr Barnes who "laid into" Christopher Harrison.
When questioned why he did not stop the attack he said: "Nobody tells the president of the chapter what to do."
During the beginning of Mr Wilkinson's defence it emerged that he told police during an interview that he was the one who had headbutted Mr Harrison, a statement which he now denies.
'Safer in prison'
During the hearing at the Old Bailey on Thursday his barrister, Andrew Selby, asked why he made the admission.
He replied: "I was so low at the time and I wanted to end my life. I thought I would be safer in prison than on the streets... I'm going to be a target after this."
Mr Wilkinson said he had gone to the Carlisle Pub in Hastings that night in February 2016 to watch a band with his wife.
He was wearing his 'Support Crew' jacket, a club run by the Hells Angels, and asked Mr Harrison, known as 'Swaggers', to join the crew but he declined.
Mr Wilkinson said he was "fine with it", but then involved Mr Barnes, to see if he could interest Mr Harrison.
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He said words were exchanged and then "Barnes laid into Swaggers head first, followed by left and right punches to the face."
If he intervened, Mr Wilkinson said, he "would have been beaten up myself there and then, I couldn't do anything about it".
Regarding his previous convictions raised earlier in the trial, he said he has a history of depression and bipolar and his crimes had "never been violent, always just verbal".
Both men deny the charges against them.
The trial continues.