The 25-year-old rapper - real name Costadinos Contostavlos - stands accused of affray stemming from accusations he was involved in a fight at a garage in Surrey, England last February (12).
The alleged victim claims the incident left him with severe facial injuries.
Contostavlos, who denies the affray charge, appeared at Guildford Crown Court in Surrey as the trial kicked off. He will be tried along with three other men - Kieran Vassell, 24, and Alfred Miller, 27, both of west London, and Kalonji Stewart, 31, from Birmingham, England.
The star told fans about his day in court by posting a picture of himself on his Twitter.com page, simply writing, "Court".