R. Kelly's 2008 Acquittal Result of Threats, Payoffs Says Michael Avenatti

R. Kelly was acquitted in his child porn case because of witness intimidation, evidence tampering, physical threats and payments to witnesses ... so claims attorney Michael Avenatti.

Avenatti does not get specific as to why he believes the various misdeeds were allegedly committed during the 2008 trial.

Kelly's current lawyer, who was not involved in the 2008 case, tells TMZ, the lawyers who repped R. Kelly had the highest integrity and Avenatti's claims are baseless.

Avenatti has been actively involved in the R. Kelly case ... he has turned over a new tape to Cook County prosecutors, which he says shows R. Kelly having sex with and urinating on a 14-year-old girl. As we reported, in the wake of the new tape, several women have come forward claiming to be victims of the singer and have been interviewed by prosecutors. A grand jury has been convened and we're told the tape and various witnesses are being presented to the panel.