The Silicon Valley trial of fallen biotech star Elizabeth Holmes was paused Friday after a juror reported possible Covid exposure, just days into what is expected to be months of testimony.

Friday's proceedings in a California court were cancelled "out of an abundance of caution", judge Edward Davila told attorneys in an online hearing late Thursday.

Holmes's trial opened Wednesday in San Jose with prosecutors claiming she told grandiose lies to cheat investors in her blood-testing firm Theranos, but her defense said her efforts were in good faith and had simply failed.

"It's a little, I don't want to say ominous, but it's of concern that before we finish the first witness we have an issue," Davila said, according to US media reports.

Elizabeth Holmes (L), founder and former CEO of blood testing and life sciences company Theranos, leaves the courthouse with her husband Billy Evans after the first day of her fraud trial in San Jose, California
Elizabeth Holmes (L), founder and former CEO of blood testing and life sciences company Theranos, leaves the courthouse with her husband Billy Evans after the first day of her fraud trial in San Jose, California AFP / Nick Otto

The juror, who reported possible exposure to the virus over the weekend prior to the trial opening, was due to get tested in the coming days.

Holmes's case has already been postponed several times -- most recently because she had a baby in early July.

When she launched the diagnostics firm Theranos in 2003 at age 19, the charismatic Holmes promised results that were faster and cheaper than traditional laboratories, running an analytical gamut on just a few drops of blood.

Trouble is, prosecutors say, the tests did not do what was promised, and she now faces fraud charges that potentially carry decades in prison.

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