The state's first trial charging undocumented immigrants with conspiracy to commit human smuggling may come to an abrupt end today for lack of evidence.

Prosecutors and defense attorneys traded arguments Monday in the trial of a Mexican national accused of being a "coyote," or human smuggler, and two others accused of conspiring with him to enter the state illegally from Mexico.

The trial tests Maricopa County Attorney Andrew Thomas' contention that the people being smuggled can be charged with conspiracy to commit human smuggling under Arizona's unique "coyote" law.

The trial is scheduled to continue until Thursday. But the question posed Monday is whether the state has sufficient evidence to continue past today. If not, the judge may throw out the charges against the defendants.

Both alleged conspirators made incriminating statements to Border Patrol agents and Maricopa County sheriff's deputies at the scene of their arrests March 2.

But under court rules, for those statements to be admitted as evidence, there must be a body of evidence independent of the statements to show that a crime took place.

Twice on Monday, Judge Thomas O'Toole of Maricopa County Superior Court said there was not.

And whether the supposed coyote's admissions to a grand jury can be allowed into evidence will be the subject of debate this morning.

Javier Ruiz Lopez, 33, is charged with human smuggling; Antonio Hernandez Lopez, 19, and Gustavo Urbalejo Gomez, 29, are charged with conspiracy to commit human smuggling.

Of the 54 suspected undocumented immigrants arrested March 2, five were never charged, 12 have had charges dismissed and 29 have pleaded guilty to a lesser charge and been returned to their native countries. Eight decided to go to trial, including the three on trial now. The rest are scheduled for trials on Aug. 1 and 11.

"These three defendants agreed to form a smuggling group," Deputy County Attorney David Rodriguez said in his opening statements. "But for their wanting to cross into the United States, this crime would not have been committed."

Ruiz, he said, was "leading a caravan into the desert" and all were "violating processes of the United States."

But that statement went to the heart of an ongoing debate in the case: whether the Arizona law against human smuggling is pre-empted by federal immigration law.

"This case is not about failure to comply with the legal processes of the United States," said Adrian Fontes, who represents Ruiz. "There is not federal seal in this courtroom. This is an Arizona state case."

The state's strongest witness is the sheriff's deputy who detained the three defendants and 51 others March 2 on a remote desert road in the westernmost part of Maricopa County.

Deputy George Burke, a 15-year veteran of the office, took the stand Monday to describe how he was making a once-weekly patrol of Hyder Gasline Road, a seldom-used dirt track, when he spotted two vans pulling on to the road from the desert. Both vans turned and went in the opposite direction when they saw Burke and then pulled off the bigger road.

Burke became even more suspicious when he noted that one of the vans bore the logo of an American furniture company but had Sonoran license plates.

He detained the occupants for an hour and a half as he waited for other deputies and Border Patrol agents to arrive. The Sheriff's Office then decided to charge them under the Arizona human-smuggling laws.

Thomas believes that the people being smuggled can be charged with conspiracy.

The Sheriff's Office has arrested about 250 people under the human-smuggling law.

According to the office's analysis, the typical undocumented immigrant arrested by deputies is a 20-something male who planned to find work in California. The majority of suspects originated from areas south of Mexico City and had never tried to cross the border before, the study said.

Even if O'Toole throws out the charges in the current trial, it will not necessarily set a precedent for other cases.

"Trials don't set precedents," Arizona State University law Professor Paul Bender said. "It's just that judge in that trial. Precedents are points of law."

However, the next two trials related to the same arrest, and the same set of facts is scheduled before O'Toole.

Attorneys representing some of the remaining defendants plan to file a special action in the Arizona Court of Appeals, claiming that Thomas' interpretation of the conspiracy laws are incorrect and that the prosecution of undocumented immigrants is pre-empted by federal law.

If the Appeals Court were to accept jurisdiction, its decision either way would set legal precedent.

Staff reporters Lindsey Collom and Richard Ruelas contributed to this article.