The shot was reportedly taken by Djibril Cisse, and chairman Niall Quinn revealed the court action on BBC radio.
“We had a supporter who got a bad injury.
“I think it was one of Djibril Cisse’s misses where he had a shot from 20 yards.
“I’m making fun of it now, but it knocked a supporter out. It was quite serious.
“That supporter is in the process of suing us right now.”