Prosecutors in Texas are seeking in excess of $1bn in damages from Johnson & Johnson in a lawsuit that alleges the pharmaceutical company overstated the safety of its anti-psychotic drug Risperdal.

The case was filed by a whistleblower, however the state of Texas joined and now more US states are launching federal cases, accusing Johnson & Johnson of illegal marketing practices.

Johnson & Johnson are alleged to have exaggerated the safety of the drug and made kickbacks in order to boost the drug’s reputation over its competitors, influencing the nation’s Medicaid program to select it for use to treat schizophrenia and bipolar disorder.

The company has vehemently denied the claims and has said it will defend itself against the lawsuit.

A jury was selected on Monday 9 January, and opening statements are due to be made to the courtroom in Austin, Texas today, with the case expected to last at least two weeks.

Whistleblower Allen Jones, formerly of the Office of Inspector General in Pennsylvania, US, originally filed the lawsuit in 2004. He alleges to have uncovered Johnson & Johnson’s actions in Texas while investigating similar claims in Pennsylvania.

Previous cases have been ruled against the pharmaceutical major, with a jury finding Johnson & Johnson guilty of violating Louisiana’s Medicaid Fraud Act in 2010, followed by a South Carolina judge ruling that the company must pay a $327m civil penalty in 2011.