Mark Stewart
![](https://i.guim.co.uk/img/static/sys-images/Guardian/Pix/pictures/2015/2/23/1424724849121/Mark-Stewart.jpg?width=100&dpr=1&s=none)
Mark Stewart is an engineer and risk analyst at the University of Newcastle in Australia. He is the co-author of Terror, Security, and Money: Balancing the Risks, Benefits, and Costs of Homeland Security and of the forthcoming Chasing Ghosts: The Costly Quest to Counter Terrorists in the United States.