Libby Wells says it's almost routine now.

She's gotten used to the "great trepidation" she feels each day when she returns home from her state job. She's good at the small details, good at watching for signs that the bars on the windows have been jimmied, the locks on the doors broken, or the burglar alarm tampered with. A widow who lives alone, she confesses that there is "always a little bit of fear" about what she might find at the end of the working day.

Her house has been robbed 15 times in the past five years. She packs a pistol to and from work.

But what makes Libby Wells' story interesting is that she does not live in a large, crime-infested city. Home is Palominas, a small and pleasant Arizona town in rural Cochise County, a mile above the Mexican border.

The location is the crux of her problem. A spurt of residential burglaries along the more isolated stretches of the border, in towns like Palominas, Bisbee Junction and Naco, have heightened tensions, spread fear and racial misunderstanding and left law officers stymied.

Some of the burglaries are the work of Mexican nationals driven by economic hardship to steal food and anything else that could help them support their families.

Cochise County sheriff Jimmy Judd says residential burglaries have become his biggest problem, one that is shared, he says, by law enforcement people along the Mexican border from El Paso to California.

Through May of this year, 238 burglaries were reported in Cochise County, and Judd says his investigations show 40 percent were committed by Mexican nationals who had illegally crossed the border. About 65 percent of the 400 burglaries reported in 1978 were blamed on illegals.

"Economic conditions are forcing many people to leave the interior" of Mexico, explains U.S. Attorney for Arizona Michael Hawkins. "Then they come to the border, many without jobs. If people get hungry enough, they'll steal."

"It's large, barren, open area that's very easy to cross. There are no natural barriers," adds Herb Walsh, who is with the border patrol in southern Arizona. "It's very easy to hop across, come on in, knock off a home that's close in the area and go back home to Mexico. And it can all be done within 15 minutes."

'at a time when Mexican nationals in the United States face problems ranging from severe economic hardships to police brutality, the rash of burglaries and the suspicions they have raised about Mexicans locally threaten to erode an already delicate relationship in many border areas.

"Since these burglaries, tension has increased tremendously," Wells said. "It's dangerous if people can't identify themselves. If they're around your property and they look like they might be an illegal alien, the word is out. It's not a good feeling. And that kind of thing never existed up until this time."

Officials and border residents fear the increased tension could lead to a repeat of the so-called Hanigan case, which involved the alleged 1976 beating of three Mexican nationals who were caught trespassing on the property of a now-deceased rancher, George Hanigan of Douglas. The three, mistaken for burglars, claimed they were tortured by Hanigan and his two sons. An all-Anglo jury cleared the men in 1977, but a national coalition of Mexican-American groups successfully petitioned the Justice Department for a reopening of the case on civil rights grounds. A grand jury in Tucson is currently questioning witnesses in the case.

"It's left the citizens in the area in the position where they're afraid to be home and afraid to leave home," says Walsh, who admits he lacks the resources to stem the flow of immigrants. "They have fencing dogs. Some people have their windows barred. It's a bad situation.

"It [the rise in burglaries] certainly has increased tensions. County officials wouldn't like to see happen, as none of us would, another Hanigan case."

While Hispanics criticize President Carter and the Justice Department for ignoring their basic needs, Anglo-Americans in the border communities make the same charge, but from a different perspective.They want more funding for the border patrol and better enforcement of existing immigration laws.

Sheriff Judd says he's "blasted the federal government for months."

"I think those folks in Washington just don't understand it," Judd said. "That border is their problem and the Mexican government's problem. It's not mine I think we better start taking care of our citizens before we start taking care of the rest of the world. And I'll tell that to Jimmy Carter if I can get ahold of him."

Except for the Hanigan episode and one well publicized rape case in 1978, violence has not been involved in any of the hundreds of incidents. Generally, food, liquor, blankets and small portable items that can be easily sold have been taken.

To allay fears and defuse tension a number of law enforcement officials and congressional staff representatives have met with citizen groups recently organized in Bisbee Junction and Palominas. At a Friday night meeting at the Palominas school, Judd announced the formation of a "Neighborhood Watch" crime prevention program, and Walsh pledged more surveillance flights by the border patrol. But the consensus was that these were stopgap measures promising only temporary solutions.

"It's always been a border problem," adds Walsh. "It ebbs and flows. There's no specific pattern although when people have no employment and no means of livelihood they are certainly more likely to come in an commit some of these crimes. There's just a tremendous number of people over there in Mexico out of work."