It also is true that building the first strong fence along the U.S.-Mexico border south of San Diego in the early 1990s, and strengthening it at the end of the decade, did coincide with a sharp drop in apprehension of illegal immigrants in the westernmost area of the U.S.-Mexico border. But analysts dispute to what extent these changes can be attributed to the border fence.
Hunter is correct that smuggling along the San Diego-Tijuana corridor dramatically decreased when the fence started to go up. Border Patrol apprehensions at the Imperial Beach station, the most secure point along the fence, dropped from 321,560 in 1993 to 19,035 in 2004, a decrease of 94 percent over the 12-year period.
But apprehensions along the entire San Diego County section of the border, which does not have a continuous secure fence, dropped sharply, too -- 79 percent between 1996 and 2002. Meanwhile, apprehensions in the neighboring fenceless El Centro County shot up during the same period.
The Congressional Research Service, a nonpartisan arm of the federal government, notes that opponents of the fence say there is no way of measuring how many smugglers go through the area without being apprehended. CRS says those same critics also point to other factors, such as a doubling of the number of border patrol agents in the same period that might have deterred illegal crossings.
Hunter is also mostly correct about his pivotal role in the construction of both the first fence along the 14-mile stretch between San Diego and Tijuana (begun in 1990) and the subsequent strengthening of the fence. He snagged the funding for the first fence in the early 1990s, then wrote the law authorizing funding for two additional layers in 1996.