On a hilltop on the Mexican side overlooking the border, a group of suspected spotters monitors the activities during a tour of the Mariposa Port of Entry. It is believed the spotters keep track of anything taking place around the ports.

They hunker down day and night on mountaintops in Arizona’s western desert, sometimes for weeks at a time.

The “scouts” or “lookouts,” as they are called, are the eyes and ears for drug- and human-smuggling cartels. And the Border Patrol is going after them.

The question is how to charge them.

The scouts have been part of cartel operations for a long time, telling smugglers when it’s safe to go and when it’s not, or guiding smuggling groups over desert trails. But with more agents and technology — and fewer border crossers — the Border Patrol has the resources to go after the lookouts, said Manuel Padilla, chief of the Tucson Sector.

“The vision is to make the Arizona-Mexico border an undesirable location for transnational criminal organizations to operate,” Padilla said.

It’s all part of a multifaceted approach, he said. The first phase is being on the ground to catch the drugs and people coming through. The second phase is breaking down the cartel’s communication and logistical network.

“How do we keep them from operating? They need two main things: the ability to move and the ability to communicate,” Padilla said. “So those are the things we target.”

But the ongoing operations don’t come without challenges.

The scouts are easy to replace, said Tony Coulson, who retired as the agent in charge of the Drug Enforcement Administration’s Tucson office in 2010.

“You might get a smuggling group to stand down in that area and go to a different route,” he said. But after a month or less, the scouts are back on that mountaintop.

He estimated several years ago that about 300 scouts operated at any given time.

The Pinal County Sheriff’s Office said in a news release last summer that the Border Patrol had identified 75 to 100 lookout posts in the smuggling corridor that runs through the county.

Logistically, taking these mountaintop scouts out is a good thing, Coulson said. But a long-term solution would involve intense coordination with investigative agencies to build good, prosecutable cases with strong prison sentences.

Otherwise, Coulson said, “if you arrest them for just immigration violations, short sentences and deportation makes these guys available to their drug organizations, so they will become scouts again because they have that skill set that needs to be used again.”

Padilla realizes the limitations of the Border Patrol.

“The Border Patrol can do one piece of it; we can do interdiction part of it,” he said. “As far as the follow-up investigation, that would depend on our investigative partners, the prosecution would depend on the U.S. attorney and the Arizona Attorney General’s Office.”

Radios, phones tossed

When agents drop down from a helicopter hovering over the mountains, everything happens very quickly.

Still, scouts typically have enough time to throw their radios or cellphones off the cliff.

Because they are rarely in possession of loads of drugs or in the company of a group of migrants, cases against them typically are based on evidence: solar panels, binoculars, encrypted radios, AR-15 rifles, carpet-soled booties to conceal footprints — and in some cases the scout’s admission.

On Oct. 2, the Tucson Sector announced a six-month counterscout operation that included 24 arrests. But nearly two months later, it’s not clear what was the fate of each scout.

The U.S. Attorney’s Office provided the Star with a case number involving five scouts it filed a complaint against on Oct. 3, which wouldn’t be included in the 24 arrests announced by the Border Patrol.

Through a federal court record search, the Star found four other cases involving seven additional scouts indicted so far this year on the same conspiracy charge — only one man was arrested before October, on Sept. 27. It is not clear if he was part of the 24.

The U.S. Attorney’s Office in Phoenix wouldn’t comment, and said it had no additional information regarding the 24 scouts. The Border Patrol said it couldn’t discuss each individual apprehension.

They were charged with a combination of conspiracy to possess less than 50 kilos of marijuana with intent to distribute, which carries a maximum sentence of five years, and with illegal entry or illegal re-entry. None of the complaints contained information that would link the scouts to specific drug seizures.

Scouts have been arrested in other operations, too.

The Pinal County Attorney’s Office has indicted more than a dozen people on similar grounds this year.

Of eight arrested in February and March by the Sheriff’s Office and the Border Patrol, five pleaded guilty to conspiracy to possess marijuana for sale, and each is serving 2½ years in prison. Another one has a trial date set for next January, and one other case is still open. A man who said he was hired to drive a van with supplies and food for the scouts pleaded guilty to one count of assisting a criminal syndicate and was sentenced to three years of supervised probation.

The Pinal County Sheriff’s Office, together with the Border Patrol, arrested another six scouts in September, and the County Attorney’s Office filed indictments under the same charge.

Conspiracy evidence

To build a solid case against scouts, prosecutors need to show the elements of conspiracy, said Pinal County Attorney Lando Voyles.

“You can argue, ‘Why did they have things like sneaky feet?’ which is very common if you are trafficking,” he said, referring to the carpeting smugglers often put on the soles of their shoes to conceal their footprints.

Although no evidence of drug possession is needed for a conspiracy case, Voyles said, it makes prosecuting the cases more difficult.

Even so, the ultimate goal is to push drug trafficking outside Pinal County, he said. “The most common committed felony in the county is drugs, whether it’s trafficking or possession.”

Regardless of the ultimate charge, Padilla said, he wants to force scouts out of business.

Even when they can’t be charged for being lookouts for cartels, the Border Patrol can deport people through a different place from where they initially crossed or charge them for being in the country illegally.

A person can get up to two years in prison for illegal entry, depending on the number of times the defendant has crossed or criminal background. An illegal re-entry charge can carry a sentence of up to 20 years if the person has been convicted of an aggravated felony. The average sentence length for illegal-re-entry offenders in 2012, though, was 19 months, according to the U.S. Sentencing Commission.

Usually are young men

Scouts tend to be men in their late teens to 30s from Mexico. Many have been in the United States illegally before. One of those indicted had been returned to Mexico voluntarily, without being officially deported, while another one had been given time served in Yuma for illegal entry before being arrested on top of a mountain.

Some of those indicted had been deported from places such as El Paso or Calexico, California.

They get paid anywhere from $100 to $800 for each smuggling group or loaded car that they help avoid law enforcement. One man said he had helped four groups in the eight to 10 days he had been on the mountaintop. Another said he was supposed to stay on top of the mountain for 30 days.

Scouts have people who fetch water and food for them who get paid separately. One 30-year-old told agents he was supposed to get paid $500 for each time the scout helped get a load through when he returned to Mexico.

A man who was stopped on Feb. 20, whose arrest led to an interdiction operation in Pinal County in February and March, said he had been paid $4,000 to pick up a van from Chandler and drive it to the Silverbell area to the drug cartel scouts.

Inside the van, deputies found 600 pounds of food, including produce and meats, in large, industrial-strength trash bags.

Only time will tell how successful the counterscout operations are. Padilla said the agency will continue to monitor how much smuggling goes on in the west desert corridor, whether agents continue to arrest the same scouts, and whether cartels change their tactics.

The harvest season for marijuana started in October and runs through the end of the year, a busy time for seizures by the Border Patrol.

“It may be that, very quickly, they stop using scouts and move to something else,” Padilla said, “or it may take awhile to be able to refine the strategies and continue to disrupt and dismantle the scout units.”

Contact reporter Perla Trevizo at ptrevizo@tucson.com or 573-4213. On Twitter: @Perla_Trevizo