Cavaliers probing Heat's signing of James

Cavs owner Dan Gilbert has hired a law firm to investigate whether the Heat violated NBA rules in their recruitment of LeBron James

CLEVELAND – The Cleveland Cavaliers have poured hundreds of thousands of dollars into a high-powered Midwestern law firm to investigate their suspicions that the Miami Heat broke NBA tampering rules while pursuing LeBron James(notes), and owner Dan Gilbert has privately vowed he won't relent until he has a thick binder of findings to drop on the desk of the NBA commissioner, league sources told Yahoo! Sports.

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The NBA won't launch an investigation into a tampering case without a formal request from a team, but sources say Gilbert's plan is to give commissioner David Stern a detailed case that includes meetings, phone calls and contingency plans that date as far back as 2008. Gilbert will implore Stern to use his powers as commissioner to get access to phone records and testimony of key people surrounding Heat president Pat Riley, James and others potentially involved.

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Gilbert will spare no expense to uncover whatever evidence he can to take to the league office, two sources with direct knowledge of the probe told Yahoo! Sports. The law firm staff includes several former prosecutors with backgrounds in investigating and constructing cases, sources said.

Prior to the start of free agency on July 1, no Miami Heat representative – including star Dwyane Wade(notes) – was allowed to discuss with James the specific circumstances around Wade, Toronto's Chris Bosh(notes) and James joining together with the Heat.

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One focus of the law firm's probe includes an alleged Riley-James meeting in Miami in November 2009, and a meeting of James' inner circle with Wade in Chicago in June 2010, sources said.

Riley, James, Wade and Bosh have denied there was a predetermined collusion in the historic free-agent binge, although the players have admitted to discussing the possibility of playing together as far back as the 2008 Olympics in Beijing.

When approached about the story on Tuesday night at Cleveland's Quicken Loans Arena, Gilbert declined to answer questions from Yahoo! Sports.

As one league source told Yahoo! Sports: The Cavs are “determined to get everything out there. They’re not letting go of this. They’re not going to just let this die."

Potential penalties for tampering could include front-office suspensions, fines and losses of draft picks. Many teams are suspicious of the league office's desire to investigate these kind of cases because of the potential embarrassment to the league.

This revelation makes for one more dramatic storyline to James' return to Cleveland on Thursday night. Gilbert escalated Cleveland's fervor over losing James when he issued a scathing email about James on the night of the two-time MVP's television decision. For that diatribe, Stern fined Gilbert $100,000.