Diddy's Former Assistant Testifies Cassie Told Him 'I Can't Get Out'

One of Diddy's former assistants recalled a couple conversations he says he had with Cassie ... including one when he says Cassie told him why she couldn't leave Diddy.

David James took the stand Monday in Diddy's federal trial and testified for the prosecution ... telling the jury he had been with Cassie in Miami early on in her relationship with Diddy.

David says he worked for Diddy from 2007 and 2009 and testified he first met Cassie on Star Island in Miami, where Diddy had rented a yacht to impress her.

He told the jury he was smoking cigarettes on a dock with Cassie ... he testified she told him, "Man, this lifestyle is crazy." David says he told her she should leave if she thought it was crazy, and says she responded, "I cant. I can't get out."

David testified Cassie told him Diddy was responsible for her career and her music, paid for her apartment, and gave her an allowance ... and he told the jury, "I didn't think she could easily leave."

David's testimony seems to line up with earlier testimony from Kerry Morgan, Cassie's former friend, who said Cassie told her she couldn't leave Diddy because he was basically in charge of her life -- namely, her job, car and apartment -- and that Cassie would've lost her livelihood if she left Diddy.

David said the second conversation happened in a taxi at the Sundance Film Festival ... where he said Cassie was super happy and wanted to tell him about a track list she came up with for a new album. He testified she started telling him about the songs, but when prosecutors asked if he remembered the album coming out, David said he did not.

Diddy's former assistant also talked on the stand about Diddy dating a bunch of women at once, though he said Diddy referred to Kim Porter as his "queen." He said Diddy once told him he had Cassie right where he wanted her, and that Cassie was "moldable."

David said he interviewed a few times to be Diddy's assistant and recalled one meeting with an HR executive from Bad Boy, who he says told him, "This is Mr. Combs' kingdom and we are all here to serve him."