Johnson & Johnson, one of the world's largest drug manufacturers, has gone on trial in a multi-billion dollar lawsuit by the US state of Oklahoma.
Prosecutors accuse the firm of deceptively marketing painkillers and downplaying addiction risks, fuelling a so-called "opioid epidemic".
Johnson & Johnson denies wrongdoing and says it marketed products responsibly.
It is the first of 2,000 cases brought by state, local and tribal governments against pharmaceutical firms in the US.
On average, 130 Americans die from an opioid overdose every day, according to the Centers for Disease Control and Prevention.
In 2017, of the 70,200 people who died from an overdose, 68% involved a prescription or illegal opioid.
In its court filing, Oklahoma alleged that Johnson & Johnson was the "kingpin" behind "the worst man-made public health crisis in [the] state's history," growing and importing raw materials which other drug-makers used for their own products.