Former Turing Pharmaceuticals CEO Martin Shkreli invoked his Fifth Amendment right against self-incrimination and declined to answer questions on Thursday from U.S. lawmakers interested in why the company raised the price of a lifesaving medicine by 5,000 per cent.

Shkreli, 32, sparked outrage last year among patients, medical societies and Democratic presidential front-runner Hillary Clinton after Turing raised the price of 62-year-old Daraprim to $750 US a pill from $13.50.

The medicine, used to treat a parasitic infection, once sold for $1 a pill. Earlier this week, documents outlined Turing's plan to turn Daraprim into a $200-million per year drug by raising the price 5,000 per cent. In documents released this week, Shkreli said in an email to one contact: "We raised the price from $1,700 per bottle to $75,000. Should be a very handsome investment for all of us."

At a hearing of the U.S. House committee on oversight and government reform, Shkreli sat at a table with arms crossed and repeatedly declined to answer questions about the effects of the price hike on patients.

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Martin Shkreli compared his interlocutors to 'imbeciles' on Twitter after his appearance where he said nothing. (Pete Marovich/Bloomberg)

"I intend to follow the advice of my counsel, not yours," Shkreli told Rep. Trey Gowdy, a South Carolina Republican. The Fifth Amendment of the U.S. Constitution says no person shall be compelled in any criminal case "to be a witness against himself."

Shkreli was arrested in December and charged with running his investment funds and companies almost like a Ponzi scheme. He has pleaded not guilty, stepped down from Turing and was fired from KaloBios Pharmaceuticals Inc.

He faces a lengthy prison term if convicted on any or all of the charges, which is why his lawyer, Benjamin Brafman, advised him to plead the fifth — a constitutional right that all Americans have, to refuse to incriminate themselves — during his appearance before lawmakers.

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Martin Shkreli invoked his Fifth Amendment privileges at a congressional hearing on Thursday. (Joshua Roberts/Reuters)

Shkreli refused to answer any questions, and at times seemed to be grinning and even suppressing laughter. Maryland Democrat Elijah Cummings repeatedly pushed Shkreli to answer, before ultimately asking him to be escorted from the hearing room once it was clear he would not answer any questions.​

Outside the room, his lawyer Brafman described his client as a "brilliant scientist" and said that once all the details come out, he will be exonerated as "not the villain or the bad boy of this story ... but a hero."

He dismissed Shkreli's gestures and facial expressions during his appearance as "nervous energy."

Despite refusing to say anything during his testimony, Shkreli took to Twitter following his appearance.

With files from Reuters News Agency