Butt has played 33 Tests for Pakistan since making his debut in 2003
By David Bond
BBC sports editor
Former Pakistan Test captain Salman Butt was investigated by the ICC's anti-corruption unit in connection with "suspicious" phone calls and texts from Mazhar Majeed during the World Twenty20 in the West Indies last May.
It has been reported before that Butt and team-mate Kamran Akmal were under investigation.
However, the BBC has learned that the ICC anti-corruption tribunal's full judgment includes fascinating evidence showing the full extent of the contact between Butt and Majeed, the agent at the centre of the affair.
The ICC provided an edited version of its full judgment on Wednesday evening, which it said was only available for seven days - and not to be accessed "for anyone located inside of England and Wales".
The evidence was not used in the ICC's case against Butt and his team-mates Mohammad Amir and Mohammad Asif, which resulted in them being banned for spot fixing by the ICC last weekend.
But the disclosure of the texts and phone calls will spark fresh fears that the links between the players and Majeed may have been much deeper than first suspected.
On their face the messages appear to reflect a pre-exisiting discussion about spot fixing
From the ICC anti-corruption tribunal's full judgment
The communications relate to 10 May, when Pakistan were in St Lucia, where they beat South Africa by 11 runs in a group match.
Previous suspicion surrounding the Pakistan team was focused on their semi-final against Australia where they lost in the final over thanks to Mike Hussey hitting three sixes in four balls.
But a source close to Salman Butt has told the BBC that the communications between Majeed and Butt in St Lucia were not evidence of any wrongdoing.
He said: "The only allegations that have been put to Mr Butt are in relation to the Tests in August and September. There is no other wrongdoing and the ICC has not charged him with anything in relation to this."
The judgment will reveal how Butt had been in receipt of what the three-man tribunal, headed by Michael Beloff QC, described as "suspicious" calls and texts from Majeed during that period.
The judgment says: "On their face the messages appear to reflect a pre-exisiting discussion about spot fixing... The episode in spring in St Lucia appears to have been the overture to the main performance in England in the summer."
The judgment's disclosure of the details from the World Twenty20 will lead to fresh questions over Butt as he considers whether to appeal against his 10-year ban, which will be reduced to five if he avoids any repeat offence and takes part in anti-corruption educational programmes.
But they will also raise issues over the ICC's investigation into other claims of spot-fixing.
Butt faces a long wait before he can resume his cricketing career
The judgment, which runs to around 90 pages, also includes the tribunal's reasons for the length of bans handed to Butt, Amir and Asif last Saturday in Doha.
This part of the document, written by Justice Albie Sachs, an anti-apartheid freedom fighter who lost an arm during "the struggle", is considered more forgiving and sympathetic towards the three players than the determination.
In it, the tribunal explains how it was unable to give bans lower than the minimum of five years, as prescribed in the ICC anti-corruption code for the most serious offence, that of fixing the result of or part of a match.
It adds that it did not press for life bans, the harshest penalty available to it, for a number of reasons.
Firstly it believed the Oval and Lord's charges were part of a one-off fix. The judgment says: "Fortunately for them an [un]promising career in spot fixing was nipped in the bud by the News of the World investigation... it was a trial run. The purpose was not to influence any outcome or to serve as the basis for betting."
The tribunal's second reason is that it could not find any evidence that monies paid to the agent Majeed were paid to the players in return for their part in the fix.
The judgment states: "We are not satisfied the monies paid were for the fix."
The tribunal also argues that because spot-fixing is less serious than match-fixing then it would have been harder to give out longer bans - even though the judgment insists the penalties given out are harsh.
"A five-year penalty is far from being a light penalty, a mere slap on the wrist," the tribunal says.
Despite that, Butt was given a tougher penalty of 10 years with five suspended because as captain he was in a position of authority. Elsewhere in the judgment he is described as "the ringmaster" and the leader of the team "for good or ill".
The judgment says: "Overall we conclude that Mr Butt's offences are more serious than that of his team-mates."
And yet, the tribunal argues that he should be given a second chance to use his leadership skills to teach younger players about the risks of corruption. Providing he takes part in such educational programmes, then he may be able to reduce his ban.
As for Asif, the tribunal also offers him the chance to rehabilitate himself with a seven-year ban possibly reduced by two years, but again it finds him guilty of a more serious offence because of his age and seniority in the team.
Despite Amir's talent - he is described as the "brightest star in the cricketing firmament" - the panel dismisses the suggestion that his potential as a Test player should be taken into consideration. But his youth and inexperience are taken into account in giving him the minimum ban of five years.
The men continue to maintain their innocence and are considering appealing against the decision.