Former US model entrepreneur Elizabeth Holmes has been found guilty of fraud against investors.

The jury found four of a total of eleven counts to be fulfilled, according to court documents on Tuesday night.

Holmes had founded the ultimately failed blood test start-up Theranos and raised several hundred million dollars from investors.

The 37-year-old had always rejected the fraud allegation and can still appeal the judgment.

Judge Edward Davila will decide on the sentence at a later date.

Theoretically, Holmes could face up to 20 years in prison per charge - however, trial observers in the USA assumed that the sentence would be much milder.

Theranos' great promise was to revolutionize blood tests: just a few drops from your finger should be enough to carry out extensive analyzes.

The total valuation of Theranos reached up to 9 billion dollars in the financing rounds, and the fortune of Holmes - who became a mother last year - was several billion dollars, at least on paper.

Compared to Steve Jobs

Holmes, who Theranos founded as a 19-year-old dropout from elite Stanford University, was hailed as a visionary.

The media compared her to Apple founder Steve Jobs - which was supported by her fondness for black turtlenecks.

Among other things, the drugstore chain Walgreens got in and sold Theranos blood tests in their stores.

As it turned out, however, Theranos technology was never sufficiently reliable.

Tests were not carried out with the company's own machines, but with laboratory technology from other manufacturers, which Theranos technicians modified on their own.

Investors and the public did not know about this.

A key problem with this method was that the machines were designed to handle larger volumes of blood from the patients' veins.

Theranos stretched the little finger samples because of this, but this led to problems with the accuracy of some tests.

According to experts, another factor was that the pressure on the fingertips when taking blood changes the composition of the samples - which can also lead to incorrect analytical values.

However, doctors use the results as an indication of possible diseases and treatments.

Theranos eventually had to widely cancel test results.

Mattis and Kissinger on the Board of Directors

The problems became known in 2015 with a series of investigative reports in the "Wall Street Journal", which Theranos initially tried to suppress with the help of lawyers. Holmes denied everything, but the articles called for US regulators, who, among other things, scrutinized the company's laboratories. Theranos had to shut down - and the donors came away empty-handed.

In a piquant twist, Wall Street Journal owner Rupert Murdoch was among the Theranos investors who eventually lost their money. But there is no evidence that he interfered with the reporting. Holmes had brought influential figures such as ex-foreign ministers Henry Kissinger and George Shultz, as well as Donald Trump's future defense minister, James Mattis, to the board of directors. They gave Therano's credibility but had no expertise in medical technology.

In the family of George Shultz, the controversy caused a rift for years.

Shultz's grandson, Tyler, who had worked intermittently at Theranos, was one of the sources of the revelations.

His grandfather stayed with Holmes for a long time afterwards.

Some donors also felt that Theranos technology was in the running for use by the US military in theaters of war.

In reality, however, explorations about this quickly ran into a dead end.

The indictment accused Holmes of deliberately duping financiers in order to get hold of the Theranos investments.

The jury saw this confirmed in three injections of money - and found Holmes guilty of conspiracy to commit fraud on another count.

Holmes testified at the trial that she sincerely believed in the technology, but that as chief executive, she was not informed of all of the problems.

For a conviction, the prosecutors had to convince the jury - eight men and four women - that Holmes misinformed investors with fraudulent intent and accepted errors in testing patients.

On three counts, the jury could not agree on the necessary unanimous vote.

The prosecutors can bring these allegations to court again.

The prosecution specifically picked the cases of two patients and six transfers from Theranos donors in the amount of between almost 100,000 and around 100 million dollars from the years 2013 and 2014.

The jury found Holmes not guilty of deliberately cheating on patients.