BOSTON (Reuters) - A federal judge on Monday declared a mistrial in the case of four former employees of a firm that advises companies on shareholder votes charged with participating in a scheme to pay bribes to learn how a proxy adviser’s clients voted.

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U.S. District Judge Richard Stearns in Boston ordered the mistrial due to a medical issue involving the wife of one of the 12 jurors hearing the case against the former employees of Georgeson LLC, a proxy solicitation firm owned by Computershare Ltd.

The four ex-Georgeson employees, Michael Sedlak, Donna Ackerly, Charles Garske and Richard Gottcent, have pleaded not guilty to wire fraud and honest services wire fraud charges.

Prosecutors had been expected on Monday to finish presenting their case after three weeks of trial. While three defendants consented to going forward with just 11 jurors, prosecutors were only willing to do so if all four agreed to that option.

David Spears, a lawyer for Sedlak, said that given the prosecution’s decision, he would seek to prevent a retrial given the U.S. Constitution’s general prohibition against being tried twice for the same crime, known as double jeopardy.

“The government’s refusal to go forward with our clients after we consented is insupportable,” Spears said.

A spokeswoman for U.S. Attorney Andrew Lelling confirmed the mistrial but declined further comment.

The trial came after Georgeson in November agreed to pay $4.5 million and enter into a deferred prosecution agreement to resolve charges that it conspired to bribe an employee of proxy adviser Institutional Shareholder Services.

Prosecutors said Brian Bennett from 2007 to 2012 used his job at ISS to supply Sedlak with information in exchange for concert and sports tickets worth $14,000, including for baseball games and U2 and Jay-Z concerts.

Sedlak forwarded the information to Ackerly, Garske, Gottcent and another Georgeson employee, Keith Haynes, prosecutors said.

Ackerly and Garske then arranged for clients to be billed for some of the bribes using false descriptions like “courier services,” prosecutors said.

The goal, prosecutors said, was to gain an illegal edge in their work helping companies shape strategies that could affect the outcome of shareholder votes.

The defendants denied wrongdoing and contended the information was not confidential.

Bennett and Haynes testified for the prosecution after pleading guilty. ISS in 2013 paid $300,000 to resolve U.S. Securities and Exchange Commission charges it failed to safeguard client information.