Former drug executive Martin Shkreli has smirked and brushed off questions about drug prices then tweeted that lawmakers were imbeciles, when he appeared at a US congressional hearing against his will.
Mr Shkreli, 32, sparked outrage last year among patients, medical societies and Democratic presidential front-runner Hillary Clinton after his company, Turing Pharmaceuticals, raised the price of the drug Daraprim by more than 5000 percent to US$750 a pill.
The lifesaving medicine, used to treat a parasitic infection, once sold for US$1 a pill and has been on the market for more than 60 years.
At a hearing of the US House Committee on Oversight and Government Reform, Mr Shkreli repeatedly invoked the Fifth Amendment of the US Constitution, which says no person shall be compelled in any criminal case "to be a witness against himself".
Wearing a sport jacket and collared shirt rather than his usual T-shirt, he responded to questions by laughing, twirling a pencil and yawning.
Committee Chairman Jason Chaffetz, a Utah Republican, asked Mr Shkreli what he would tell a single, pregnant woman with AIDS who needed Daraprim to survive, and whether he thought he had done anything wrong. Mr Shkreli declined to answer.
"I intend to follow the advice of my counsel, not yours," said Mr Shkreli after South Carolina Republican Representative Trey Gowdy suggested he could answer questions that were unrelated to pending fraud charges against him.
After the hearing, Mr Shkreli's lawyer, Benjamin Brafman, attributed his client's behaviour to "nervous energy".
Later, though, Mr Shkreli wrote on Twitter: "Hard to accept that these imbeciles represent the people in our government."
US Representative Elijah Cummings, who learned about the tweet while Turing Chief Commercial Officer Nancy Retzlaff was testifying, pounded his fist on the dais. The Maryland Democrat then shouted about an internal Turing document in which a staffer joked about the price increase.
"You all spent all of your time strategising about how to hide your price increase ... and coming up with stupid jokes while other people were sitting there trying to figure out how they were going to survive," Mr Cummings said.
Mr Shkreli was arrested in December and charged with running his investment funds and companies almost like a Ponzi scheme.
He has pleaded not guilty to the fraud charges, which are not related to the pricing of Daraprim. He also stepped down from Turing and was fired from KaloBios Pharmaceuticals Inc.