The killing of Arizona rancher Robert Krentz allegedly by an illegal immigrant has some critics pointing out that hundreds of miles of U.S.-Mexico border fencing isn't even high enough to stop a person on foot.
Of the 646 miles of barriers currently constructed along the 2,000-mile southern border of the United States, 300 miles are vehicle barriers, according to the Department of Homeland Security. That means they're meant to keep out cars and trucks, but aren't high enough to keep out people crossing the border illegally on foot.
Fencing in place just south of the Krentz family ranch in southeastern Arizona is exactly that kind of vehicle barrier, plus there's a sizable gap in the fence nearby.
Residents and officials say the security barrier is simply ineffective, and that the killing last month is shining a light on the problem.
Rancher Wendy Glenn, Krentz's longtime friend and neighbor who heard the man's last radio transmission to his brother, said she has roughly 4 miles of border fence along Malpai Ranch. The "wildlife-friendly" barrier -- one that allows large animals and determined people to pass through freely -- ranges from large Normandy-style "X" crosses to standard posts and rails, topping off at no more than six feet high, she said.
"It doesn't keep any people out," Glenn told FoxNews.com on Monday. "We don't want any more fence here. We want more people on the border. No matter what they put in, they're going to tunnel under, cut through, or use ladders. We don't need that."
Glenn characterized the border fence as a "big waste of money" and called for increased federal presence along the remote areas, as well increased communication among law enforcement agencies.
"We need more people on the border," she said. "And we need more horse patrols -- they are awesome."
Jenny Burke, a spokeswoman for U.S. Customs and Border Protection, said 646 of approximately 670 miles of pedestrian and vehicle border fencing has been constructed as of March 26. Just six miles of fencing infrastructure remains to be completed along the 2,000-mile U.S.-Mexico border, Burke said.
The roughly 1,350 miles that will not be protected by a border fence of any kind will be patrolled by border agents, other infrastructure or technology, Burke said, or a combination of all three.
Pedestrian fencing used along the border is determined by the geography and have several variations, including steel picket-style fences set in concrete, blockades similar to those found around federal buildings and concrete walls with steel mesh. Vehicle fences, meanwhile, are about 6 feet tall and are typically large Normandy-style crosses.
"And they're all welded together," she said. "So they're impossible to move."
Burke said areas selected for physical fences are locations where illegal immigrants could easily blend in with local surroundings if those individuals successfully crossed the border.
During a tour of the border along Fort Hancock, Texas, last week, Border Patrol Agent Joe Romero said security in the area was improving despite rising fears in the community that drug cartel-related violence in El Porvenir, Mexico, could spill over into the U.S. town at any moment. Still, threats remain, he said.
"At no point am I going to indicate that we have full control of the border, or that we're 100 percent secure on the border," Romero told FoxNews.com. "It's still a struggle, there's still some work to be done. But we've made huge strides."
Romero, one of about 2,600 U.S. Border Patrol agents scouring the 125,000-square mile El Paso sector, extending from Fort Hancock to the New Mexico-Arizona state line, said apprehensions in the area have fallen approximately tenfold in the last four years, from roughly 122,000 in fiscal year 2006 to about 15,000 last year.
The border fence in Fort Hancock roughly 50 miles southeast from Ciudad Juarez, the epicenter of Mexico's ongoing drug war, stands about 20 feet tall in some areas and is entirely absent in others. And along some stretches of land between Fort Hancock and Tornillo, Texas, the nearest town, all that separates the U.S. and Mexico is the ankle-deep Rio Grande River.
Despite its perception as a cure-all blockade, Romero said the border fence is meant to deter large groups of illegal immigrants from entering the country illegally. It's also meant to slow down any would-be border-crossers, giving crucial seconds to roving border patrols in trucks, all-terrain vehicles and on horseback.
Former Colorado Republican Rep. Tom Tancredo, whose touchstone issue is illegal immigration, told FoxNews.com the federal government needs to ideally have a "layered" fence along with National Guard patrol along the entire southern border. A layered fence is a barrier that includes a fence, a road and another fence.
But he said the hundreds of miles of fencing along the border now are not effective.
"That's what's so maddening," Tancredo said.
"It doesn't stop people," said Charles Heatherly, executive director of Tancredo’s Rocky Mountain Foundation. "It's a lie."
Heatherly said in an e-mail to FoxNews.com that the kind of fence by Krentz's home is incapable of stopping "drug smugglers like the one who killed Rob Krentz."
It's unclear who killed Krentz, but local authorities said they suspected an illegal immigrant since footprints near the scene of the crime led back to the Mexican border.
FoxNews.com's Judson Berger contributed to this report.