Riz Khan speaks with an American army interrogator who participated in the abuse of hundreds of prisoners in Abu Ghraib and Fallujah.

In his just-released book, Fear Up Harsh: An Army Interrogator's Dark Journey Through Iraq, Tony Lagouranis speaks about his struggle with his conscience and how he decided to break the silence surrounding torture by American forces.

Lagouranis had learned Arabic and joined the army as an interrogator before the events of September 11, 2001. After the Iraq war, he was sent as part of a special intelligence-gathering task force that roamed around the country.

He speaks about the "culture of abuse" that he found in Iraq, and the confusion among American soldiers as to whether Iraqi prisoners were subject to any legal protections. He also describes his use of military dogs to terrorise prisoners.

The term "fear up harsh" is an official tactic designed to terrify prisoners into revealing information. Lagouranis was the first US army interrogator to denounce the tactics and question American actions abroad.