(Source: Arizona Department of Corrections) Richard Stokley was convicted of murdering two teen-age girls in rural Cochise County two decades ago.
Richard Stokley (then), Mandy Meyers
U.S. Supreme Court justices are being asked to block an Arizona death-row inmate's scheduled execution Wednesday on grounds that he's being unfairly punished in comparison with another man convicted of the same crime.
Richard Dale Stokley was convicted of first-degree murder in the 1991 killings of two 13-year-old girls in rural Cochise County.
Co-defendant Randy Brazeal was released from prison last year after serving a 20-year term imposed under a plea agreement for second-degree murder.
Stokley's lawyers argue that it violates his constitutional rights to be days away from execution while Brazeal is free despite being at least equally responsible.
Stokley confessed to raping, strangling and stabbing one of the girls and dumping her body down a water-filled mineshaft.
Brazeal, who was 19 at the time, turned himself in to authorities in Chandler the day after the girls were killed, claiming Stokley held him hostage while he raped and murdered the girls.
But Stokley claimed Brazeal was a willing participant and assisted in killing the girls to cover up their crimes.
Officials have said Brazeal got a plea deal because prosecutors were afraid he could be acquitted if they had to go to trial before DNA evidence was available.
If the Supreme Court agrees to hear the case, Stokley's execution would be put on hold indefinitely.
Copyright 2012 CBS 5 (Meredith Corporation). All rights reserved. The Associated Press contributed to this report.