Quincy Jones Testifies -- Joe Francis Is a LIAR!!! There Was No Murder Plot

Quincy Jones just testified ... he NEVER saw an email from casino mogul Steve Wynn threatening to kill "Girls Gone Wild" honcho Joe Francis -- despite Francis' claims he was the target in a Wynn murder plot.

TMZ broke the story ... 79-year-old Quincy was subpoenaed to testify in Steve Wynn's defamation lawsuit against Francis, in which the "GGW" creator has claimed Wynn threatened to kill him and have him buried in the desert over a gambling debt Francis owed to Wynn's casino.

According to Francis, Quincy had seen an email from Wynn describing the alleged murder plot -- so Wynn called on Quincy to testify in order to show Francis was lying.

And Quincy didn't disappoint -- taking the stand today, claiming he never heard Wynn threaten Francis ... let alone saw an email detailing murder plans.

The questioning lasted mere minutes -- with Wynn's lawyer even trying to lighten the mood, asking Quincy, "So I hear you're in the music business."

Quincy laughed, replying, "65 years ... that's all."