Jurors weighing the fate of fallen US biotech star Elizabeth Holmes on Monday told the judge they cannot agree on verdicts for three of the fraud charges against her.

The 12-person panel did not signal its decisions on the remaining eight counts Holmes faces over her once billion-dollar startup Theranos, in a case seen as an indictment of Silicon Valley culture.

The 37-year-old could be jailed for years if convicted over what prosecutors argued was a willful conning of investors and patients.

Holmes's startup vowed to revolutionize diagnostics with self-service machines that could run an array of tests on just drops of blood, a vision that drew high-profile backers and made her a billionaire by the age of 30.

The jury in the trial of Elizabeth Holmes say they are deadlocked on three of the 11 charges against her
The jury in the trial of Elizabeth Holmes say they are deadlocked on three of the 11 charges against her AFP / Nick Otto

Federal Judge Edward Davila on Monday instructed jurors to continue their deliberations, saying there was no hurry.

The judge has the option of accepting the verdicts reached by the jury, and declaring a mistrial regarding counts on which they cannot unanimously agree.

It would then be up to prosecutors whether to seek a new trial on those charges.

Monday was the seventh day of jury deliberations.

Holmes was once hailed as the next tech visionary, and collected mountains of investors' cash, but her empire collapsed after Wall Street Journal reporting revealed the testing machines didn't work as promised.