Attorneys for John Allen Muhammad released a May 2008 letter on Wednesday in which the mastermind of the deadly 2002 sniper attacks in the Washington, D.C., area proclaims his innocence.

The rambling, handwritten letter was made available because of requests for a statement from Muhammad, his attorneys wrote on the Web page of their law firm. The letter was filed in federal court in connection with Muhammad's unsuccessful attempt to block his execution, the attorneys said.

Muhammad, 48, is scheduled to die by injection on Nov. 10 at a Virginia prison.

In the letter dated May 8, 2008, and rife with misspellings, Muhammad writes of discussions with a new team of attorneys and of assurances that "exculpatory evidence" that he claims was withheld from his trial "will prove my innocent and what really happen ...."

The letter adds: "So all you police and prosecutors can stand-down-'rushing' to murder this innocent black man for something he nor his son (Lee) had nothing to do with ...."

Lee Boyd Malvo was Muhammad's teenage accomplice, who is serving a life sentence. Muhammad fostered a father-son relationship with Malvo but the two were not related.

Jonathan Sheldon, one of Muhammad's attorneys, wrote in an e-mail to The Associated Press that the letter has been filed in U.S. District Court since May 2008. "It just had not come to public attention, like much of our filings," he wrote.

The letter, written under the heading "Attorney Client Privilege," was apparently filed during an attempt by lawyers to spare Muhammad from the death penalty.

In their filing, the lawyers said Muhammad was regularly whipped with hose pipes and electrical cords and beaten with hammers and sticks by family members during a brutal childhood.

Muhammad was convicted of killing Dean Harold Meyers at a Manassas, Va., gas station during a three-week spree that killed 10 in October 2002. The killings happened in Maryland, Virginia and the District of Columbia.

Tuesday, Muhammad's attorneys asked the U.S. Supreme Court to stop his execution.

Muhammad's lawyers also have asked Virginia Gov. Timothy M. Kaine for clemency, saying Muhammad is mentally ill and should not be executed.