Early this year we learned that 50 Cent was going to have to go to trial for leaking a sex tape involving Lastonia Leviston, Rick Ross's baby mama.

This happened back in 2009 when Fif was feuding with the man he liked to call Officer Ricky. To mock Ross, he put the tape of Leviston and another man on YouTube with the male talent's face blurred and 50 offering up narration.

Leviston alleges 50 befriended her under false pretenses and then got the tape from the guy in the video. She's seeking legal damages from Fif because she says she was so distraught after the tape went online she contemplated suicide.

However, 50 is now suing Ross saying he -- not 50 -- was the one who originally leaked the tape. 50 wants Ross to have to pay some or all of any judgement against him in the Leviston lawsuit because Ross is ultimately responsible for the unauthorized amateur porn getting out.

Leviston and 50's trial was set to begin on Tuesday. No word on when the 50-Ross trial will start.