Texas elections law says state prison inmates who are appealing their convictions are eligible to register. Many lawyers and voting rights advocates were unaware of the rule.

The U.S. Supreme Court will hear the case of a Texas man on death row who has long argued that DNA testing would help prove he didn't kill an 85-year-old woman during a home robbery decades ago.

The death row inmate, Ruben Gutierrez, appealed a lower court's ruling against his challenge to a Texas law limiting the use of DNA testing after a person has been convicted of a crime. The Supreme Court is due to hear the case during its new nine-month term that begins on Monday.

Ruben Gutierrez was sentenced to death for the 1998 Brownsville murder of an elderly woman. His execution was stayed in July.