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In just one week, some of Mexico's most high-profile corruption cases have unraveled on thin or made-up evidence, reinforcing long-held notions that the Attorney General's Office is more focused on political vendettas or favors than justice.

Two of the cases against public servants, a former drug czar and a former No. 2 in the Defense Department accused of links to drug cartels, were thrown out within days last week. In one, the judge determined that witness testimonies were false, and the other case dissolved because prosecutors couldn't find evidence to support the charges.

Many blamed the failed prosecutions on the administration of former President Felipe Calderon, which prepared the cases.

Experts say the failed prosecutions are the product of a justice system dominated by political interests, and hindered by questionable police work and deficiencies in organization. Some cases lose credibility because they are deemed to involve political payback or favors, while others are undermined by shoddy investigations done in the heat of the moment.

"There is a deficiency in the organization, in the presentation of investigations. There are serious technical flaws," said Javier Oliva, a researcher at the National Autonomous University of Mexico who studies defense and security. "If the question is, 'Why did these cases fail?', it is because they have no legal support."

Mexico's new government led by the Institutional Revolutionary Party, or PRI, also has more quietly dropped another case that arose during Calderon's term — this time seeming to take the opportunity to wash its hands of a big corruption case that could be embarrassing for the PRI.

Federal prosecutors turned the case linked to former Coahuila state Gov. Humberto Moreira, a PRI politician who saw $3 billion in public funds go missing during his tenure, over to local prosecutors in his home state, where his brother is now governor. The case was aimed at two of Moreira's close associates who were discovered with unexplained wealth, including his state treasurer at the time who is now wanted in the U.S. on money-laundering charges. An Attorney General's Office official, who was not authorized to speak publicly, said he didn't know why federal prosecutors decided they had no jurisdiction.

In the release of two high-ranking drug war officials last week, President Enrique Pena Nieto's government was keen to show the evidence against them was flawed. The now free men claimed publicly that they had been the targets of political retribution by the former Calderon administration and saved by the PRI, which returned to power last year after a 12-year hiatus.

The two cases were once touted as proof of Mexico's new fortitude in fighting internal corruption, and their end came five years after a justice reform that was supposed to bring fairness and transparency.

The first to be set free was former anti-drug prosecutor Noe Ramirez, who was arrested in 2008 in an internal sweep known as "Operation Clean House" on charges that he took $450,000 a month in cash from the Beltran Leyva drug cartel.

Samuel Gonzalez, who served a decade before Ramirez in the top anti-drug post, said the case against Ramirez was launched after the 2008 arrest of Gerardo Garay, then the country's acting federal police chief, for stealing money from a Mexico City mansion during a drug raid.

Garay's boss and ally, federal Public Safety Secretary Genaro Garcia Luna, was reportedly incensed by the arrest and demanded that Calderon prosecute someone at the Attorney General's Office in revenge, Gonzalez said.

"Garcia Luna was the one who demanded that Calderon go after Noe Ramirez, because charges had been brought against Garay, he wanted someone of the same level charged," Gonzalez said.

Then Attorney General Eduardo Medina Mora, now Mexico's ambassador to the United States, did not respond to a request for comment.

Two days after Ramirez was freed, retired army Gen. Tomas Angeles Dauahare was also ordered released after the Attorney General's Office decided to drop a drug corruption case against him. Angeles Dauahare, a former assistant defense secretary, told The Associated Press that he believes the case against him was political.

Angeles Dauahare had openly criticized Calderon's strategy of going after drug cartels and appeared at a May campaign event for Pena Nieto. Days later, he and other senior military leaders were arrested on accusations of helping members of the Beltran Leyva cartel.

"They tried to destroy everybody who didn't share their opinions," Angeles Dauahare said. "The Attorney General's Office was used to carry out this reprisal."

Some say a major error by prosecutors is that they largely rested their accusations on the testimony of protected witnesses, without verifying independently if additional evidence existed.

Both Ramirez, the drug czar, and Angeles Dauahare, the general, were arrested on the testimony of a protected witness known as "Jennifer," a former associate of the Beltran Leyva cartel who is now in the U.S., according to trial documents.

Records from Ramirez's case obtained by the AP suggest prosecutors inserted false dates into witness statements. The judge said that accounts from people in Mexico's witness-protection program were unreliable when he announced his decision to absolve him.

As the case unfolded, prosecutors scrambled to gather whatever evidence they could against Ramirez, even reportedly calling U.S. agents to see if they had anything on him.

One former U.S. law enforcement official, who couldn't speak on the record for security reasons, said such requests were not uncommon.

Mexican officials "would detain someone and then call us up and say, 'Do you have anything on him?," the former official said. "It was arrest first and ask questions later. This isn't against their law, not out of the ordinary. That's the system."

He agreed with Oliva, the university researcher, that prosecutors lack investigative skills and have difficulty building a case.

Current Attorney General Jesus Murillo Karam told local media that his office will launch an investigation into "Jennifer" and the cases involving the witness's false testimony.

Another case that concluded embarrassingly was that of an alleged plot to smuggle the son of late Libyan dictator Moammar Gadhafi into Mexico as his regime crumbled. Calderon's office had bragged about the "careful intelligence work" that dismantled the complex scheme in the months leading up to Mexico's 2012 presidential election.

Two of the suspects, Cynthia Vanier of Canada and Gabriela Davila Huerta of Mexico, were released from custody last week after three judges determined that much of the evidence against them was collected illegally and that their basic rights were violated.

Murillo has said publicly several times that he inherited a justice department in disarray and is reviewing previous cases as part of a reorganization and cleanup.

After nearly five months at the helm, he has yet to release details of the reorganization.

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Adriana Gomez Licon on Twitter: http://twitter.com/agomezlicon