District attorneys in Las Vegas declined to prosecute a sexual assault claim against Cristiano Ronaldo. Nicola Campo/LightRocket via Getty Images

Police matched a DNA sample from Cristiano Ronaldo to evidence from an alleged 2009 rape at a Las Vegas hotel, but detectives struggled with uncooperative attorneys for his accuser before prosecutors declined to pursue a criminal charge, according to correspondence obtained by Outside the Lines.

In emails between Clark County (Nevada) prosecutors and Las Vegas police, detectives expressed frustrations about attorneys for Ronaldo's accuser, Kathryn Mayorga.

"Communicating with the victim is now impossible and her attorney Les Stovall is extremely challenging," Las Vegas detective Jeffrey Guyer said in a March 28 email to prosecutor Jacob Villani.

The district attorney's office said on July 22 that it was declining to prosecute Mayorga's sexual assault claim because the allegation "cannot be proven beyond a reasonable doubt."

Mayorga's attorneys did not respond to requests for comment Thursday, and the DA's office told Outside the Lines, "We have no additional comments beyond what was in our statement originally released on July 22."

According to court documents, Mayorga signed a 2010 confidentiality agreement with Ronaldo in exchange for a $375,000 hush-money payment. Ronaldo's lawyers have said Ronaldo and Mayorga had consensual sex in his suite at a Las Vegas casino hotel but deny it was rape.

Prosecutors say the initial police investigation in 2009 was closed after police were stymied by lost evidence and lack of cooperation from the accuser.

Mayorga, 35, asked police to reopen the case in August 2018. After months of investigation, detectives appeared less than confident of making a case, according to correspondence obtained by Outside the Lines.

"Aside from the obvious issues regarding a 10 year cold case, involving an extremely high-profile suspect, a previous secret civil agreement, and a victim who immediately discloses material to international journalists," Guyer wrote, noting other "sticking points," including difficulty communicating with Mayorga's attorneys and obtaining documents related to her settlement or her more recent civil lawsuit.

"I have repeatedly asked the victim for the above listed documentation, however she does not have and cannot provide it," Guyer wrote to Villani on March 20.

At one point in the correspondence, Villani suggested getting a grand jury subpoena if one former Mayorga attorney didn't respond to requests for information about her settlement.

Police also were unable to authenticate leaked documents about the case that have been published in the European media. The documents, stolen by a Portuguese hacker and published by the group known as Football Leaks before details turned up in the German magazine Der Spiegel, purportedly included Ronaldo's admission that he had sex with Mayorga against her will. Ronaldo's agent denied the report.

Guyer wrote that it was "impossible to determine which documents have been altered or which ones are legitimate."

"In my opinion, even if [the hacker] discloses he obtained the documents and sold them unedited, it's impossible to authenticate their validity without Ronaldo's attorney or a witness present when Ronaldo purportedly answered these questions," the detective wrote.

Police also struggled to get cooperation from British police related to a 2005 rape allegation against Ronaldo, according to the correspondence.

According to a March 20 email from Guyer, INTERPOL confirmed to Las Vegas police that Ronaldo was accused Oct. 1, 2005, of raping a woman and was arrested 18 days later.

Guyer informed prosecutors on May 29 that Scotland Yard, INTERPOL and police in Manchester, England, "refuse to provide the police report or victim's information."

"The details they released are the victim reported the incident in London but the sexual assault occurred in Manchester," he wrote. "Ronaldo was arrested 10/19/2005 and posted bail. The case did not proceed through court and was dismissed three weeks later."

Guyer added that neither Scotland Yard nor Interpol had "located any reported sexual assaults throughout Europe."

Las Vegas police were successful, through a U.S. Justice Department attaché in Rome, in getting Ronaldo to submit a DNA swab that matched evidence in the case.

"Yeah DNA is back and is a match," Guyer wrote March 8.

According to a June 4 email, Mayorga met with Las Vegas police. Guyer summarized the meeting and said Mayorga stated she had identified Ronaldo to police in 2009 as the man who assaulted her, but she also said that at the time, she "was insistent she did not want to move forward with prosecution."

Police and prosecutors have both disputed she disclosed Ronaldo's name in 2009.

By early July, Guyer was ready to send prosecutors a request for prosecution.

"Thank you for your hard work on this investigation," chief deputy district attorney James Sweetin wrote to Guyer on July 3. "Based on my conversations with you, as well as my review of the documents and information obtained in your investigation, I can't think of a rock you left unturned."

Less than three weeks later, prosecutors announced the decision not to pursue the case. They have not responded to questions about the case or their decision.

Mayorga's civil case against Ronaldo alleges conspiracy, defamation, breach of contract, coercion and fraud. Her complaint seeks unspecified monetary damages greater than $50,000. This month, Ronaldo's lawyers asked a judge to declare that the 2010 agreement is still in effect and move the case to out-of-court mediation.

Outside the Lines producer Nicole Noren and The Associated Press contributed to this report.