NASHVILLE (AP) — James Earl Ray doubted a jury would believe a defense proposal to blame a conspiracy for the assassination of the Rev. Martin Luther King Jr., according to letters he wrote to his lawyer as he tried to win a trial and withdraw his own guilty plea in the 1968 slaying.

The letters are among documents going up for auction in Tennessee from the estate of the late Jack Kershaw, a Nashville attorney who represented Ray in the mid-1970s.

Ray pleaded guilty in Memphis in 1969 to killing the civil rights leader and was sentenced to 99 years in prison, but recanted the confession three days later. He died in prison in 1998. Kershaw died in 2010.

In one letter, Ray responds to plans by one of his other attorneys to write a book alleging white racists conspired with government agencies to kill King.

"Conversely what I have learned based on what evidence in this area we have, whites of that persuasion were most likely not in volved and while that type allegation would naturally appeal to the large publishing companies, (I) am concerned that if their (sic) were not considerable evidence in support, the allegation might not be taken well with the type persons who sit on juries," Ray wrote.

The transcript was released by Case Antiques Inc., Auctions & Appraisals, which will sell the documents at auction Jan. 28 in Knoxville.

In one of the papers, Ray also discussed his media image:

"One of my problems, I believe, with interviews is that I attempt to look at the case from a legal standpoint while the reports apparently want to hear the emotional statements (not guilty- framed_persecuted_sob-sister routine)."

Ray, who was white, claimed as he sought a trial that he was forced into pleading guilty. But news accounts at that point showed that the judge asked him five times if his plea was voluntary.

Ray also claimed after his confession that a mysterious man named "Rao ul" was responsible for the slaying. However, Ray's fingerprints were found on the rifle used to kill King as the civil rights icon stood on a balcony at the Lorraine Motel.

The slaying set off riots across the country. Years later, the King family said it supported a trial for Ray, and King's son Dexter said he believed Ray was innocent of the crime.

The Ray archive carries a presale estimate of $8,000 to $10,000, the auction house said. Papers, photographs and audiotapes from the estate will be auctioned.