By Bill Cotterell and Jon Herskovitz
TALLAHASSEE, Fla./ AUSTIN, Texas (Reuters) - Two U.S. death row inmates face execution on Tuesday, including a Florida man convicted of a 1991 sexual assault and murder who will be put to death using a new lethal injection procedure that has drawn legal challenges.
The executions of Darius Kimbrough in Florida and Jamie McCoskey in Texas would be the 33rd and 34th executions in the United States this year, according to the Death Penalty Information Center, a national nonprofit organization.
Texas has carried out the highest number of executions in 2013 with 14, followed by Florida with six.
Kimbrough, 40, was sentenced to die in 1994 for killing Denise Collins, an aspiring artist, after he broke into her Orlando, Florida, apartment and sexually assaulted her. She was found barely alive on her bathroom floor in October 1991. Collins died days later of head injuries suffered in a beating that broke her jaw and fractured her skull.
Kimbrough, 18 at the time, was convicted of raping another Orange County woman six months later.
He was sentenced to 10-1/2 years in prison and DNA evidence from the attack was used to link him to the Collins murder.
Kimbrough made a handwritten plea to the Florida Supreme Court questioning the use of the DNA evidence and a new sedative being used in executions in the state. The high court last week rejected his letter asking for an opportunity to raise doubts about the new lethal injection procedure.
His execution would be the second in the state using midazolam as the first of three drugs administered in lethal injections.
The sedative, known commercially as Versed and commonly used as sedation for minor procedures, was adopted by Florida officials after the state reported dwindling supplies of pentobarbital, a barbiturate. The shortage was due to a decision by the drug's manufacturer to clamp down on sales for its use in executions, prison officials said.
Last month, seven Florida death row inmates sued the state, arguing midazolam was not an anesthetic. But a judge dismissed their legal challenge, which claimed that the drug left inmates aware of their surroundings but unable to speak or move and in extreme pain in their final minutes.
Citing security reasons, prison officials have refused to say what tests or laboratory data assured them that midazolam would prevent inmates from feeling pain when the second and third drugs - a paralytic agent and a heart-stopping drug - are administered.
Capital punishment opponents have challenged use of midazolam, claiming it might allow suffering that violates the Eight Amendment prohibition of "cruel and unusual" punishments.
In the Texas case, McCoskey was convicted of kidnapping a couple in 1991 in Houston, raping the woman and stabbing her fiancé to death.
Lawyers for McCoskey, 49, have told media they are not planning any last-minute appeals.
The victims were Michael Dwyer, 20, and his 19-year-old fiancée, whose name was not listed on the Texas Department of Criminal Justice's website because she was a rape victim. She survived the assault and identified McCoskey in a police line-up.
Texas has executed 506 prisoners since the reinstatement of capital punishment by the U.S. Supreme Court in 1976, the most of any U.S. state.
The executions are scheduled for 6 p.m. local time in each state.
(Writing by Kevin Gray; editing by Colleen Jenkins and Maureen Bavdek)
(This story was refiled to clarify details of Florida inmate's arrest, and removes incorrect reference to neighbor and handyman, paragraphs 4-6)