Nearly half of terrorists crossing into the U.S. to perform violent acts or making an escape from the country afterward were American citizens, and a significant percentage were Canadians, find a Homeland Security Department-funded study.

According to Fierce Homeland Security, the National Consortium for the Study of Terrorism-conducted study is based on data gleaned from terrorist court cases from 1980 through 2004 showing that 264 individuals during that period with a direct tie to terrorism crossed a U.S. border in relation to a terrorist act. The article also reports that of the 95 individuals for whom citizenship was determinable, 48 percent were U.S. citizens, while another 18 percent were Canadian citizens.

Border security managed to thwart just 13 percent of the crossings, and terrorists’ preferred port of entry was airports – land ports of entry or seaports were a minority of the total, the article reports.

Only a minority of the indicted terrorists had a previous known arrest record: 11 percent were previously arrested in the U.S.; 11.1 percent were previously arrested abroad.

States along the southwest border – California, Arizona, New Mexico and Texas – accounted for only six of the 115 cases for which location crossing data was available. (The report does note that this data only includes border crossings specifically referenced in the federal terrorism cases’ court documents; it’s possible that the data could be nonrepresentative.)