English was not the only language used in the jury deliberation room in Conrad Murray's case ... this according to a relative of one of the jurors ... and there may have been a language barrier in the juror room.
We're told at least 2 of the jurors began discussing the case in Spanish during the 8-hour deliberation.
A relative of one juror -- we'll call him juror A -- tells TMZ ... another juror -- juror B -- had "some trouble" understanding some of the testimony. During the deliberations juror A had to translate the testimony into Spanish to juror B.
In the questionnaire jurors were required to fill out, the first question read, "Do you have any difficulty reading, speaking or understanding English."
A spokesperson for the court tells TMZ ... no juror ever requested a court-appointed translator at any time during the trial or deliberations.