A sex tape involving  R.Kelly and a baseball star's wife -- which self-styled community activist Derrick Mosley is accused of using in an extortion attempt -- does exist, a prosecutor said Tuesday.

The government initially cast doubts over whether there was a sex tape, which Mosley demanded $20,000 to destroy. But Assistant U.S. Attorney Virginia Kendall said Tuesday at Mosley's detention hearing that investigators found the tape during a search of his home.

Mosley, 38, was charged last week with attempting to extort New York Yankee's player Gary Sheffield and his gospel-singing wife, DeLeon Richards. Richards and Kelly had a relationship before Richards married Sheffield.

U.S. Magistrate Judge Morton Denlow ruled Tuesday that Mosley should be kept behind bars, despite pleas from two of Mosley's brothers, Donnell and Dwayne, who defended their younger brother.

As Denlow questioned his brothers, Derrick Mosley looked away, put up his clasped hands to hide his face and later wiped away tears. His brothers vouched for him, saying their younger brother is a talented musician, a church man who would show up to his future court hearings. But neither could put up property to ensure Mosley would not violate term s of his release.

But Kendall said Mosley had a gambling problem and that the Illinois Department of Revenue had banned him from entering the Elgin riverboat casino because he was begging for money. She said Mosley has financial problems and had just cashed a $35,000 grant meant to start a children's at-risk program -- though the government didn't know what he did with the money. Mosley's attorney said it is in his residence.

Kendall also said Mosley owed the government about $26,700 from a previous bank fraud conviction.

She argued the tape's existence was all the more reason to keep Mosley behind bars, saying he intended to do harm and was dishonest when he told Sheffield's agent, Rufus Williams, that he had destroyed it. In a secretly recorded conversation, Mosley scoffed when Williams offered $1,000 for the video and suggested $20,000.

Kendall described Mosley's alleged conduct as "not an aberration but an escalation of behavior," ticking off various crimes he had committed since he was 20, from theft to writing bad checks. She said he was repeatedly given second chances and was on supervised release when the feds charged him with extortion.

Mosley's attorney, Luis Galvan, said that after his client was arrested, Mosley voluntarily offered to turn over the tape to prosecutors but the government chose to seize it with a search warrant.

"I continue to see this case as one person's negotiation is another person's extortion," Galvan said.

Denlow disagreed, saying Mosley is accused of severely disrupting the lives of others because of the publicity the case received. He also said he couldn't be assured Mosley wouldn't continue the behavior while he awaits trial.

Credits: Natasha Korecki/ Chicago Sun Times