Suge Knight -- Sneaks Courtroom Birthday Message To Son

Suge Knight pulled a fast one in court Tuesday ... waiting for the TV camera to move in his direction and seizing the opportunity to wish his 6-year-old son Legend happy birthday.

Suge's appearance in his murder case was routine, but as the lawyers and the judge did housekeeping business, the famous defendant used his ingenuity to communicate with Legend.

Suge's had very little contact with the boy since being jailed back in January and his attorneys are fighting to give him more visitation.

This birthday's a lot different from last year's ... Suge spent the day with Legend at Disneyland.