AceShowbiz - Farrah Fawcett and Ryan O'Neal's troubled son is facing a costly lawsuit from the man who accused him of a violent knife attack.

Redmond O'Neal was charged with attempted murder after an alleged series of random attacks in Los Angeles last month, and now, one of his alleged victims has opened up about an assault, claiming O'Neal stabbed him in the head and slit his throat "along the carotid artery".

The man claims he has suffered great mental and physical pain and nervous system damage as a result of Redmond's actions and he believes his injuries will leave him with a permanent disability.

He's suing O'Neal for damages and medical expenses related to his injuries.

Meanwhile, Redmond stands accused of seriously injuring five people. He's facing charges of attempted murder, two counts of assault with a deadly weapon, brandishing a knife, battery and criminal threats.