In light of the failure of the police to adequately investigate the case before settling on a suspect, the highly suggestive identification procedure and the contaminated identifications it produced, and the failure to give the jurors the tools needed to properly assess the evidence, it is not surprising that Troy Davis was convicted.  

And, for precisely those reasons, it should come as no surprise that so many independent witnesses ultimately recanted.

There were nine witnesses who implicated Troy Davis at trial - Redd Coles, Darrell "DD" Collins, Kevin McQueen, Jeff Sapp, Larry Young, Harriet Murray, Dorothy Ferrell, Antione Williams, and Stephen Sanders. Every witness - save Redd Coles and Sanders - has since recanted, two attempted to do so at trial.  See various briefs discussing substance of recantations.

Recantations Were From Independent Witnesses

As the prosecutor was so quick to point out at trial, the vast majority of the now-recanting witnesses did not know Troy Davis "from a sack of salt!"

McQueen, Young, Murray, Ferrell, and Williams had no prior connection to Troy Davis and, thus, no motive to hurt him then or help him now.  Moreover, with the exception of Young and Murray, these witnesses did not have a connection to one another.  Finally, their recantations were staggered over a considerable period of time belying any claim of collusion; McQueen recanted on December 5, 1996; Ferrell on November 29, 2000 (first attempted at trial); Collins on July 11, 2002 (also attempted at trial); Young on October 11, 2002; Williams on October 12, 2002; Murray on October 14, 2002; Jeffrey Sapp on February 9, 2003.

Evidence of Police Intimidation & Perjured Testimony at Trial

Two of the seven recanting witnesses actually attempted to recant at trial.  At the trial, Darrell "DD" Collins, who was sixteen years old at the time of his original statement to the police, testified that he was interrogated for hours and threatened with arrest.  It was under those circumstances that he provided a statement implicating Troy Davis.  Collins “told [the detective] what he wanted to hear” “cause [he] was scared, [and] didn’t want to go to jail.”  T. 1135, 1145.  The police told him “if I don’t cooperate with them, that I’m gonna be in prison for ten to twelve years.”  T. 1135.  And within a few hours of her testimony, Ferrell admitted she committed perjury when she testified earlier that day.