Defense attorney Steve Sadow presented the video during a surprisingly brief cross-examination of Birkhead.
Birkhead made the video with Smith four days after the American Music Awards show in which her slurred speech raised questions about whether she was under the influence.
"People thought I was drunk, on drugs, losing it," Smith said on the video that Birkhead said was broadcast on TV. "I'm not losing it, America. I'm fine, happy."
It was the jury's most extensive look at the demeanor of Smith and the first time her voice was heard in the drug conspiracy case denying she was on drugs.
Birkhead previously testified about his concerns that Smith was taking too many prescription medications on a regular basis.
The night before the awards show, he said, she suffered a seizure and was almost too sick to go on. He said he urged her to cancel, but she insisted on going forward. He said he didn't see her take any drugs that night.
Smith said on the video shot by Birkhead that she was shocked when the calls began coming after the AMA show asking if she was under the influence during the performance.
Among those who eventually called, according to testimony, was her doctor, /*Sandeep Kapoor*/, who was worried she might have been taking too many prescription drugs.
Smith's lawyer-boyfriend /*Howard K. Stern*/, who is represented by Sadow, Kapoor and /*Dr. Khristine Eroshevich*/ have pleaded not guilty to conspiring to provide the former Playboy Playmate with massive doses of drugs.
Authorities claim that 44 different medications were prescribed for /*Smith*/ under a number of other names, including Stern's.
The autopsy showed that the 39-year-old had nine different medications in her system.
They aren't accused of causing her 2007 overdose death.
The Associated Press contributed to this report.