Kamil Abu al-Hail, an Iraqi ex-MP, accused the 15 aides of Saddam Hussein of crimes against humanity has said he was falsely imprisoned for months.
Kamil Abu al-Hail said he had been held at a prison in Baghdad, where hundreds were beaten and tortured daily.
The defendants are on trial for allegedly helping to suppress a Shia uprising after the 1991 Gulf War.
Kamil Abu al-Hail said that he had been arrested after arriving in Baghdad to attend a parliamentary session in the aftermath of the uprising, and taken to al-Radwaniya prison.
"I heard screams of pain as prisoners were beaten and tortured.
At the end of the day, I could see people being carried out on blankets soaked with blood. They could not walk because of the harsh torture."
Mr Abu al-Hail was released several months later, after receiving a presidential pardon.
"I was dismissed from the parliament. My cotton factory and my house were destroyed by the shelling from the army."
The Shaaban Intifada (Uprising) started in March 1991 as defeated Iraqi troops fled back to southern Iraq after US-led forces took control of Kuwait.
Many Shia blame the US for the uprising's failure, as it came to a ceasefire agreement with the Iraqi government and did not intervene.
The trial continues.