As an unembedded freelance journalist in Iraq, I have safely driven through scores of American roadblocks all over this country. I have also spent many hours with U.S. troops as they set up and operate these checkpoints.

At the same time, like other reporters here who don't travel with armies of their own -- and like the millions of Iraqis who either have some money or are brave enough to participate in their country's reconstruction -- I live constantly with the fear of being kidnapped. We see every day the damage done with the millions of dollars that Iraq's Baathist and Wahhabist insurgencies make from that appalling business.

So as investigators try to sort out how U.S. troops could have fired on a car carrying newly freed Italian journalist Giuliana Sgrena, wounding her and killing the man who secured her release, I'm thinking about how checkpoints save lives. We don't know exactly what happened at the checkpoint on the way to the Baghdad airport. But I've seen how checkpoints work, and the American soldiers who man them are anything but trigger-happy. They know the consequences of making a mistake...