The Guardian | Tom Dart in Dallas @Tom_Dart

A white Toyota Sequoia pulled up behind a Range Rover in an upscale shopping mall near Dallas-Fort Worth international airport at 6.47pm on 22 May 2013. A man exited the bulky SUV and walked to the passenger side of the Range Rover. He fired repeatedly at his target with a 9mm pistol and the Sequoia sped off.

The episode took six seconds.

On Monday, nearly three years after Juan Jesús Guerrero Chapa was murdered while out buying shoes with his wife, two men are scheduled to stand trial in Fort Worth on charges related to his death in a case that could shed fresh light on Mexican drug cartel activities and structure both south and north of the border.

Osiel Cárdenas Guillén, the former leader of the Gulf cartel, will be called to testify as a defence witness according to a court document. He was sentenced to 25 years in federal prison in 2010 for crimes including drug dealing, money laundering and murder threats, and forfeited $50m in illegal gains. He was captured in 2003 and extradited in 2007 to the US, where he is serving his sentence at a federal “supermax” prison in Colorado.

Cárdenas’s plea deal with US prosecutors prompted a war between the Gulf cartel and the Zetas, its former enforcement wing, unleashing waves of violence inMexico and along the border that killed thousands.

The deal also made Guerrero Chapa into an even more important figure in Gulf cartel, a recent Dallas Morning News investigation found.

Guerrero Chapa was originally Cárdenas’s lawyer, but after his boss’s arrest he became the de facto head of the Gulf cartel, lawyers for one of the defendants in the forthcoming trial allege in court documents.

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“Chapa ran a large criminal enterprise whose activities included murders, narcotics trafficking, kidnapping, extortion, bribery, money laundering and torture,” they claim, arguing this meant he had a “large number of enemies”.

But all the while, Guerrero Chapo was living in the US on a visa and was an informant for the US government. Cárdenas is expected to give details on Guerrero Chapa’s role in cartel activities.

Jesús Gerardo Ledezma-Cepeda, then 58, and his son, Jesús Gerardo Ledezma-Campano, then 30, were arrested in September 2014 at a border checkpoint bridge over the Rio Grande. The other defendant, José Luis Cepeda-Cortés, a legal US resident, then 58, was detained at a nearby home.Charges against the three relatives include interstate stalking resulting in death – an accusation that suggests authorities believe they facilitated the murder but were not the direct assassins. An attorney for Ledezma-Cepeda did not respond to a request for comment.

Ledezma-Campano, a former police officer in Monterrey, Mexico, pleaded guilty last month at a secret hearing and will testify against his father and his father’s cousin, NBC local news reported. The US attorney’s district office did not respond to a request for comment.

Court filings last month claim that Guerrero Chapa, who was 43 at the time of his death, believed he was in danger. He received phone calls warning he “needed to be on his guard” and told his wife he feared for his life, telling her that the men hunting him knew where he lived and the couple should stop using their cellphones. Defence lawyers dispute this, contending that since the autopsy report showed cocaine in Guerrero Chapa’s system he had not cut off contact with criminals for self-protection.

The bloody and sudden end to Guerrero Chapa’s life, gunned down as he sat in the passenger seat of his vehicle while his wife loaded their shopping, was the culmination of a long and detailed surveillance operation.

The accused made trips from Mexico to north Texas starting more than two years before the murder to track Guerrero Chapa in a meticulous fashion, according to the partially redacted criminal complaint.

It states that they rented homes and exchanged information about his family and residence over email, changed vehicles frequently so Guerrero Chapa would not become suspicious and set up a camera to record his car when it left his million-dollar home in Southlake, 20 miles from downtown Fort Worth.

Investigators found a tracking device on the Range Rover’s chassis – one of six devices they said were linked to the same account.

“We’ve always known that there are operations in the United States,” said Nathan P Jones, a Mexico studies researcher at Rice University’s Baker Institute and author of a book on Mexican drug networks. “They operated in a much more low-profile fashion, that’s why you don’t see the levels of spillover violence that you do in places in Mexico. For the most part it’s pretty limited and you’d expect it to operate in the way that you’re seeing it operate here: if there are significant disputes you would expect low-profile hitmen to track their targets for a prolonged period of time.

“The one thing that would be unexpected for me is why did they kill this guy in public? My question would be, did something happen where they were suddenly rushed, because if they’re so professional why did they do it in a place with surveillance cameras?”

Two years earlier the plan was seemingly to get Guerrero Chapa back to Mexico, where it would be easier to silence him and escape justice. A man with drug links named Lus Lauro Ramírez-Bautista was also looking for Guerrero Chapa and gave Ledezma-Cepeda $38,000, court filings state. The prosecution argues he had photos of Guerrero Chapa’s house when he was stopped at the border in March, 2011, and told authorities that Guerrero Chapa was a drug dealer who should be deported to Mexico.

“The statements made by Ramírez-Bautista at the time of his stop at the border were designed to enlist the assistance of the government in returning Chapa to Mexico so that Ramírez-Bautista and others could kill him,” assistant US attorney Joshua Burgess claimed in a court document.

Cárdenas’s sentencing in Houston in 2010 took place amid intense security and considerable secrecy.

For this trial, the federal district judge, Terry Means, denied prosecution requests to seal the jury instructions but agreed to seal the government’s exhibit list, keeping it off the public record.

While the prosecution is likely to try to tie the defendants to other murders to emphasise their dangerousness, while stressing Guerrero Chapa’s seniority, the defence is expected to probe his relationships with US authorities during his time as an active cartel figure – unless government attorneys can persuade the judge to limit the scope of the testimony and keep sensitive information out of the public record.