Seven years after Spanish investigators uncovered one of cycling's most sophisticated and widespread doping networks, some of its central figures will finally stand trial on Monday in Madrid's Criminal Court. The case, in which 35 witnesses are called to testify, is scheduled to last until March 22, 2013.

Judge Julia Santamaria will preside as six defendants are tried. They include doctors Eufemiano Fuentes and Yolanda Fuentes, brother-and-sister suspects at the heart of a complex blood-doping ring that stained cycling's reputation in Europe.

Also on trial will be medical doctor Jose Luis Merino and former ONCE and Liberty Seguros team sports director Manolo Saiz. Vicente Belda and Ignacio Labarta, both associated with the former Kelme team, will also be on trial.

Many riders will be called to testify as witnesses, including two-time Tour de France champion and current Team Saxo-Tinkoff rider Alberto Contador.

Cyclists will not be on trial because Santamaria can only rule on matters covered by Spanish law as it applied in May 2006, when police raids uncovered a mass of evidence in labs, offices and apartments in Madrid, Zaragoza and El Escorial.

This limitation means the scope of the trial can only focus on charges relating to actions that could "endanger public health." But that doesn't mean the trial won't lead to new revelations about athletes who cheated to get an unfair advantage.

"If one of the defendants says that, for example, he injected a certain athlete, then Spain's anti-doping agency or a sports federation could open an investigation to see if they could be subject to a ban," spokesman for the state prosecutor's office Eduardo Esteban said.

Miguel Angel Adan, spokesman for Spain's anti-doping agency, confirmed the body was studying the possibility.

According to documents reportedly seen by sports newspaper AS, defense lawyers will argue that Fuentes and his co-defendants did not endanger cyclists' health because they relied on the best technology available.

The proceedings will be followed closely by the World Anti-Doping Agency, which pushed for the case to go to court and will be a party to the trial along with the International Cycling Union (UCI), the Italian Olympic Committee, the International Association of Professional Cycling Teams, and former cyclist Jesus Manzano.

WADA is disappointed the trial is limited to cycling, as athletes from other sports were also implicated.

"We have expressed our frustration, but at least we are finally getting a hearing," WADA director general David Howman explained and added "The case was originally canned, but we pushed and insisted to get it reopened. Our expectations are limited, but our hopes are high."

"There were athletes from a number of sports involved," Howman explained and added "The doctor is on trial. We need to hear what he was practicing and who his patients were."

Among evidence seized were code names allegedly referring to individual riders, refrigerators stocked with numbered blood and blood plasma bags and a virtual pharmacy of performance-enhancing substances including EPO, human growth hormone, steroids and testosterone -- many of the things Armstrong admitted to using in his interview with Oprah Winfrey.

The Puerto case implicated more than 50 cyclists - including Contador, Ivan Basso, Jan Ullrich and Alejandro Valverde - in the use of performance enhancing substances or practices.

The most high-profile witness is Contador, who was stripped of a third Tour de France title and banned for two years for testing positive for clenbuterol en route to winning the 2010 Tour de France.

Contador has since had to negotiate with the UCI and the Court of Arbitration for Sport about the size of the fine to be paid when the court rejected his assertion that the positive doping sample he provided originated from eating contaminated beef.

Contador is scheduled to testify on February 15. Contador is refusing to comment on the case ahead of the Operation Puerto trial.

Hampered by the legal shortcomings of the trial, particularly that suspects cannot be charged retroactively for doping crimes, Spanish judges have twice tried to drop the case.

These actions have scarred Spain's reputation for combating doping just as Madrid is bidding to host the 2020 Olympics.

"Justice shouldn't be this slow. It manifests the inefficiencies of the Spanish judicial system," Esteban said. "This case in particular has taken far too long. It was difficult to place the events (under investigation) within the legal framework existing at the time, because blood isn't medicine. It generated a lot of doubts that had to be cleared up."

The government has since taken action to criminalize doping and current Sports Minister Jose Ignacio Wert has said legislation is making its way through parliament.

If found guilty of endangering athletes' health, the defendants could stand to lose their professional licenses and face two years in jail. They could avoid jail time and receive suspended sentences, Esteban said.

Valverde is the only Spanish rider who has been punished based on Operation Puerto evidence. German cyclist Ullrich chose retirement in the face of the police discoveries and Italian cyclist Basso's implication led to a two-year ban.

Valverde was banned worldwide after a CAS panel accepted WADA and UCI arguments that he doped with the blood-boosting hormone EPO and was connected to the Operation Puerto investigation. Valverde led cycling's world rankings when his suspension was confirmed in 2010.

At the heart of the case is the process of blood doping or blood packing.

Fuentes allegedly stored bags containing high concentrations of hemoglobin-rich red cells taken from the riders' own blood so it could be re-injected in competition when they needed a performance boost.

Bags were labeled with codes, some based on the names of riders' dogs. Basso was "Birillo," Jorg Jaksche of Germany was "Bella."

Although he denied it, Valverde owned a dog called Piti, the arbitration court heard. And Piti was the code on a bag containing blood plasma which DNA tests confirmed was his.

Fuentes is alleged to have used centrifuges to separate red blood cells from the plasma they normally float in, enabling riders injected with them to enjoy a significant boost.

Manzano, one of the plaintiffs, is a retired cyclist who turned whistleblower after suffering medical problems he said were caused by doping practices he was submitted to by Eufemiano Fuentes while riding for team Kelme.

Given Operation Puerto's history, Manzano is not optimistic about the trial's outcome, reiterating WADA's complaint that there were athletes from other sports who were clients of Fuentes yet to be named.

"I don't have many hopes, with the judges having opened and closed the case so many times," he said and added "There are 100 bags of blood that nobody knows who belong to, and many other things, including a lot of (performance enhancing) products. There are things which sadly we will never know."