Holmes is facing 11 counts of fraud for allegedly defrauding investors out of millions as she was developing her blood-testing startup. She has pleaded not guilty. If convicted, she could face decades in prison.
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"What we really heard from her in the last two days is a scene-setting, we've heard about her life in Houston, dropping out of Stanford to change the world with her revolutionary technology," said ABC News Correspondent Rebecca Jarvis. "What we got today was more on that technology."
In a fully packed courtroom, Holmes began her testimony answering questions about how the company's blood-testing device was supposed to work. She admitted to her defense attorney Kevin Downey Theranos attempted to partner with the Department of Defense before the deal fell through.
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"There was a lot of ambition to have a relationship with the Department of Defense, but she clearly said in her testimony today that partnership never materialized," said Jarvis.
Throughout the hearing, Downey asked Holmes specific questions about clinical studies Theranos did with pharmaceutical companies like Merck and AstraZeneca - as well as the company's involvement with Pfizer.
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Defense attorney Holden Green says looking back using great detail is a common defense strategy aimed to build credibility among jurors.
"I believe she's just trying to lay the groundwork that she was an entrepreneur and trying to find a way to do something better and more efficient," said Green, a 21-year veteran defense attorney who's worked in both state and federal court.
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Green says he's not surprised Holmes maintained a calm composure throughout questioning citing it's a common technique used by defense teams.
"In the end the jury are people and they have to like how you talk and your presence," Green said.
Jarvis agreed adding Holmes' confidence during questioning even came with lightness or softer tone in her voice.
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"There was never a point where Elizabeth seemed tongue-tied or questioned what she was going to say," Jarvis said.
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Green says if Holmes continues to perform well on the stand, it's possible the prosecution's cross-examination set to resume following Thanksgiving weekend may take longer.
"I just can't imagine it will take less than a couple days because they know they could lose this case on how well she testifies," Green said.
Holmes is set to testify for the third time Tuesday morning before the trial breaks for the holiday recess.