THE Hells Angels bikie accused of gunning down a good samaritan who went to the rescue of a woman being assaulted may have been high on ice at the time of the fatal shooting.

A Melbourne court was also told yesterday that star Collingwood AFL player Alan Didak would be a key witness in the case against accused killer Christopher Wayne Hudson.

But Mr Hudson's lawyer told the court that Didak's "credibility is very much an issue".